Current Affairs 1 October 2026: Today's GK & MCQs

The correct answer is D, Tenth Schedule. The Tenth Schedule carries the anti-defection provisions, so a legislator who deserts the party on whose ticket he or she was elected can be disqualified under it. The schedule was inserted by the 52nd Constitutional Amendment Act of 1985 and applies to members of Parliament and of the state legislatures alike. A member loses the seat for voluntarily giving up party membership or for voting against the party whip, and the presiding officer of the House decides such a case. A merger escapes disqualification only when at least two-thirds of the members of that legislature party agree to it. A is wrong because the Second Schedule fixes the salaries and allowances of the President, Governors, judges and other high offices. B is wrong because the Fifth Schedule deals with the administration of Scheduled Areas and Scheduled Tribes. C is wrong because the Eighth Schedule lists the recognised languages of India. Exam tip: link the pair - Tenth Schedule with the 52nd Amendment of 1985.

The correct answer is A, Argentina, Mexico, South Africa and Turkey. All four of these countries sit in the G20, so this is the only group in which no name falls outside the forum. The G20 began in 1999 as a meeting of finance ministers and central bank governors, and it was raised to the level of a leaders' summit in 2008 after the global financial crisis. It brings together nineteen countries along with the European Union, and the African Union was admitted as a member at the New Delhi summit. Its Asian members include India, China, Japan, South Korea, Indonesia, Saudi Arabia and Turkey. B is wrong because Malaysia and New Zealand are not members, even though Australia and Canada are. C is wrong because Iran and Vietnam stand outside the group, while Brazil and Saudi Arabia are inside it. D is wrong because Singapore is not a member, though it is often invited as a guest. Exam tip: among the Southeast Asian states only Indonesia is a G20 member.

The correct answer is D, Fundamental Duties. Upholding and protecting the sovereignty, unity and integrity of India is listed as a duty of every citizen, so the provision sits among the Fundamental Duties and not in any other part. The Fundamental Duties were added as Part IVA, Article 51A, by the 42nd Constitutional Amendment Act of 1976 on the recommendation of the Swaran Singh Committee; ten were added then and an eleventh, on the education of children, came with the 86th Amendment of 2002. They are moral obligations and cannot be enforced by a court on their own. A is wrong because the Preamble speaks of the unity and integrity of the nation as an ideal but lays no duty on a citizen. B is wrong because the Directive Principles address the State, not the citizen. C is wrong because Fundamental Rights are claims a citizen holds against the State. Exam tip: Article 51A came with the 42nd Amendment, 1976.

The correct answer is C, 2 - 4 - 1 - 3. Mahendravarman I came first, Gopala next, then Bhoja and finally Parantaka I, which is exactly this order. Mahendravarman I ruled the Pallavas of Kanchi in the early seventh century and is remembered for the rock-cut temples at Mandagapattu and for his play Mattavilasa Prahasana. Gopala was raised to the throne of Bengal around the middle of the eighth century and founded the Pala dynasty. Mihira Bhoja led the Gurjara-Pratiharas of Kannauj in the second half of the ninth century, at the height of the tripartite struggle. Parantaka I of the Cholas ruled in the early tenth century and defeated the Pandyas at Vellur. A is wrong because it places Bhoja before Gopala. B and D are wrong because both begin with Parantaka I, the latest of the four rulers. Exam tip: the sequence runs Pallava, then Pala, then Pratihara, then Chola.

The correct answer is D, none of the statements given above is correct. Every one of the three descriptions gets a detail wrong, so the fourth option is the only one left. Lok Adalats are organised under the Legal Services Authorities Act of 1987 to settle disputes by compromise, and their award is treated as a decree of a civil court against which no appeal lies. A is wrong because a Lok Adalat takes up both a case already pending before a court and a dispute at the pre-litigation stage. B is wrong because it can settle a compoundable criminal offence as well as a civil dispute; only a non-compoundable offence is kept out. C is wrong because a Lok Adalat is made up of a serving or retired judicial officer together with other persons, usually a social worker and a member of the legal profession. Exam tip: remember the Act of 1987 and the rule that a Lok Adalat award is final, with no appeal.

The correct answer is B, the Government is responsible to the Parliament and can be removed by it. A parliamentary system rests on the executive answering to the legislature, so the council of ministers stays in office only while it keeps the confidence of the House. India took this form from Britain: the ministers are drawn from the legislature, they are collectively responsible to the Lok Sabha under Article 75, and a no-confidence motion carried against them brings the whole ministry down. The President is the nominal head while the Prime Minister is the real head of the executive. A is wrong because a government of all parties is a national or coalition arrangement, not a feature of the system itself. C is wrong because the people elect the legislature, and it is the legislature that makes and unmakes the government; direct removal by voters belongs to no Indian office. D is wrong because a fixed term the House cannot cut short describes the presidential system. Exam tip: parliamentary means responsible government, presidential means fixed tenure.

The correct answer is C, 1 and 3 only. Statements 1 and 3 hold while statement 2 does not, so this pairing is the right one. The Agreement on Trade-Related Investment Measures is one of the World Trade Organization agreements that came out of the Uruguay Round in 1995. It bars a member from placing conditions on a foreign investor that distort trade in goods, and the two named prohibitions are the local content requirement and the trade balancing requirement, which is why a quantitative limit on what an investor may import is not allowed. The agreement covers investment measures only insofar as they affect trade in goods, so statement 2 is wrong; services are handled separately under GATS. Statement 3 stands because the agreement does not tell a country whom to admit as an investor or on what terms, and so does not regulate foreign investment itself. A and D are wrong because each includes statement 2. B is wrong because it rests on statement 2 alone. Exam tip: TRIMS is about goods, GATS about services, TRIPS about intellectual property.

The correct answer is C, Ishwar Chandra Vidyasagar. Vidyasagar served as the secretary of the Hindu Female School, and the school was renamed after John Elliot Drinkwater Bethune, who had founded it in Calcutta in 1849. Vidyasagar was the strongest voice for the schooling of girls in nineteenth century Bengal; as an inspector of schools he opened dozens of girls' schools in the districts, and his campaign against the misery of widows led to the Hindu Widows' Remarriage Act of 1856. He also pressed for an end to child marriage and to polygamy. A is wrong because Annie Besant worked in India half a century later and is tied to the Central Hindu College at Banaras and to the Home Rule League. B is wrong because Debendranath Tagore led the Brahmo Samaj and founded the Tattvabodhini Sabha. D is wrong because Sarojini Naidu belongs to the freedom struggle of the twentieth century. Exam tip: pair Bethune School, 1849, with Vidyasagar as its secretary.

The correct answer is C, Lokayata and Kapalika. Neither of these belongs to the six orthodox systems, so this is the pair that stands outside. The six systems, called the Shad Darshanas, are Samkhya, Yoga, Nyaya, Vaisheshika, Mimamsa and Vedanta, and all six accept the authority of the Vedas. They are usually learnt in three pairs: Samkhya with Yoga, Nyaya with Vaisheshika, and Mimamsa with Vedanta. Lokayata is the materialist school also called Charvaka, which rejects the Vedas, the soul and life after death, and is therefore counted as heterodox along with Buddhism and Jainism. Kapalika was a Shaiva tantric sect, a religious order rather than a school of philosophy. A is wrong because Mimamsa and Vedanta are the two schools built on the Vedas themselves. B is wrong because Nyaya supplies Indian logic and Vaisheshika its atomism. D is wrong because Samkhya and Yoga form the oldest pair among the six. Exam tip: orthodox means Veda-accepting; Charvaka, Buddhism and Jainism are the three heterodox schools.

The correct answer is A, 1 only. Only the first statement holds, so the other combinations fall away. India follows single citizenship and a single domicile, which means a person is a citizen of India alone and not separately of a state, unlike the United States where a citizen also belongs to a state. Citizenship is dealt with in Articles 5 to 11 and in the Citizenship Act of 1955, which allows it to be acquired by birth, descent, registration, naturalisation or the incorporation of territory. Statement 2 is wrong because Article 58 asks only that a candidate for President be a citizen of India; a citizen by naturalisation is equally eligible. Statement 3 is wrong because the Act provides for loss of citizenship by renunciation, termination and deprivation, and a naturalised citizen can be deprived of it for fraud or disloyalty. B, C and D are wrong because each of them includes one of these two mistaken statements. Exam tip: single citizenship, single domicile - and Articles 5 to 11 are the citizenship articles.

The correct answer is B, 1 and 2 only. Ajanta and Lepakshi both carry painting on their walls and ceilings, while Sanchi does not, so the first two alone fit. The Ajanta caves in Maharashtra hold the finest surviving Buddhist murals in India, painted in the tempera technique between the second century BCE and the fifth century CE, with the Bodhisattva Padmapani and the Jataka scenes among the best known. The Veerabhadra temple at Lepakshi in Andhra Pradesh is covered with Vijayanagara murals of the sixteenth century, including the large ceiling panels of Shiva and the vividly painted Nataraja. A is wrong because Lepakshi is left out of it. C is wrong because Sanchi in Madhya Pradesh is famed for its stupas and for the carved gateways of its toranas, which is sculpture, not painting. D is wrong because two of the three places do have murals. Exam tip: Ajanta stands for painting, Sanchi for sculpture on stupa railings and gateways.

The correct answer is D, the level of mutual trust and harmony in the society. Social capital means the networks, shared norms and trust that let people in a society work together, so it is measured by relationships rather than by things or numbers of people. The idea was popularised by Robert Putnam, who argued that a community rich in trust and civic association gets better government and faster growth because agreements are kept without costly enforcement. Self-help groups, cooperatives and village committees are the everyday form it takes in India. A is wrong because literacy is part of human capital, the skill and knowledge embodied in people. B is wrong because buildings, infrastructure and machines are physical or produced capital. C is wrong because the size of the working age group is the demographic dividend, a matter of population structure. Exam tip: physical capital is what you build, human capital is what you learn, social capital is whom you trust.

The correct answer is A, an investor who feels that the price of a particular security is going to fall. A bear expects prices to slide and therefore sells, hoping to buy the same security back cheaper, which is why a falling market is called a bear market. The name is said to come from the bear striking downward with its paws, against the bull that tosses its horns upward. On Indian exchanges a bear typically sells short, and a spell of heavy selling that drags prices down is called a bear hug or a bear raid. B is wrong because an investor who expects prices to rise is a bull. C is wrong because a person holding a share or a bond and so having an interest in the company is a stakeholder. D is wrong because one who lends money or buys a bond is a creditor. Exam tip: bear sells expecting a fall, bull buys expecting a rise; Dalal Street carries statues of both.

The correct answer is D, neither 1 nor 2. Both statements describe the two offices wrongly, so neither can be accepted. A jagir was an assignment of the land revenue of a tract, given to a mansabdar in place of a cash salary for military and administrative service, not for judicial and police duty; the holder collected the revenue due and kept troops from it. Jagirs were transferable and were shifted every three or four years so that no noble struck roots in one district, and they lapsed to the emperor on the holder's death, so statement 1 is wrong. A zamindar, by contrast, held a hereditary right in the soil of his locality, collected revenue from the peasants and passed on the state's share while keeping a commission called nankar, so the hereditary part of statement 2 is exactly reversed. A, B and C are wrong because each accepts at least one of these two flawed statements. Exam tip: jagir was transferable and not hereditary, zamindari was hereditary and rooted in the locality.

The correct answer is B, its unprofitability in the world market because of new inventions. Indigo lost its market when chemists learned to make the dye in a factory, so the Indian crop became unprofitable and cultivation shrank. Adolf von Baeyer worked out the structure of indigo in the eighteen eighties and the German firm BASF began selling synthetic indigo in 1897; within a few years it had taken most of the world trade, because the manufactured dye was cheaper and of a steadier quality than the plant extract. Bengal and Bihar, which had lived on indigo exports, saw acreage collapse in the first decade of the twentieth century. A is wrong because the Indigo Revolt of 1859 in Bengal and the Champaran satyagraha of 1917 checked the planters in particular districts but did not end the industry. C is wrong because national leaders raised the cultivators' grievances, not a case against the crop. D is wrong because the Government protected the planters rather than curbing them. Exam tip: synthetic indigo from Germany, 1897, killed the natural dye trade.

The correct answer is A, 1 only. The National Green Tribunal Act rests on the right to a healthy environment read into the right to life, so only the first provision is in point. The Supreme Court has held in a line of cases, from Subhash Kumar onward, that Article 21 includes the right to a clean environment, and the Act of 2010 was passed to give that right a forum of its own. It set up a tribunal with judicial and expert members which decides civil cases on environmental laws within six months, and it drew on the Stockholm and Rio declarations, to which India was a party. Statement 2 is wrong because Article 275(1) provides grants in aid for the administration of Scheduled Areas and has nothing to do with the tribunal. Statement 3 is wrong because Article 243A concerns the powers of the Gram Sabha under the panchayat provisions. B, C and D are wrong because each of them takes in one of these two irrelevant articles. Exam tip: NGT Act 2010, Article 21, five benches with the principal bench at Delhi.

The correct answer is A, 1 and 2 only. The Act of 1813 broke the Company's trade monopoly and asserted the Crown's sovereignty, but left the revenues where they were, so the first two statements stand and the third does not. The Act came at the height of the free trade campaign in Britain: it threw the India trade open to all British merchants, keeping the monopoly only in tea and in the China trade, which was ended by the Charter Act of 1833. It also declared in plain words that the Crown held sovereignty over the Indian territories the Company governed, and it set aside one lakh rupees a year for education and allowed missionaries into India. Statement 3 is wrong because the Company continued to control and spend Indian revenues; Parliament supervised through the Board of Control rather than taking the purse. B and D are wrong because each includes statement 3. C is wrong for the same reason and also drops statement 2. Exam tip: 1813 opened trade except tea and China; 1833 ended the monopoly altogether.

The correct answer is C, only two pairs. Dignaga and Nathamuni are matched rightly while Aryadeva is not, so exactly two pairs are correct. Aryadeva, who lived about the third century, was a Buddhist monk of the Madhyamaka school and the chief disciple of Nagarjuna; his Chatuhshataka defends the doctrine of emptiness, so calling him a Jaina scholar is wrong. Dignaga, of the fifth or sixth century, founded the Buddhist school of logic and wrote the Pramanasamuchchaya, which shaped debate on perception and inference for centuries. Nathamuni, of about the tenth century, was the first acharya of the Srivaishnava tradition at Srirangam; he gathered the Tamil hymns of the Alvars into the Nalayira Divya Prabandham and was the grandfather in the line that led to Ramanuja. A is wrong because two pairs do match. B understates the count and D overstates it. Exam tip: Nagarjuna, Aryadeva, Buddhapalita and Chandrakirti all belong to the Madhyamaka line.

The correct answer is B, 2 only. The second statement describes the two bodies correctly while the first gets the origin of the Board wrong, so only statement 2 can be accepted. The National Green Tribunal is a specialised court set up by the National Green Tribunal Act of 2010 to decide disputes under the environmental laws quickly, and it does take such cases away from the ordinary courts. The Central Pollution Control Board works on the quality of air and water, promoting the cleanliness of streams and wells, laying down standards and running the national monitoring network. Statement 1 is wrong because the Board was also created by a statute, the Water (Prevention and Control of Pollution) Act of 1974, and not by an executive order; the Air Act of 1981 later added to its work. A and C are wrong because each accepts statement 1. D is wrong because statement 2 is sound. Exam tip: CPCB 1974 under the Water Act, NGT 2010 under its own Act.

The correct answer is D, Neolithic. Piklihal and Utnur are South Indian Neolithic settlements, famous for the ash mounds their cattle-keeping people left behind. Piklihal lies in Karnataka and Utnur in Telangana, and both were excavated in the 1950s. Their people tamed cattle, used polished stone axes and handmade grey pottery and lived in circular huts, which places them in the Deccan Neolithic phase of roughly 2500 to 1000 BCE. The ash mounds are the burnt remains of heaped cow dung from cattle pens, a feature almost unique to this region. A is wrong because monolithic simply means made of a single large stone and is not an archaeological period. B is wrong because megalithic sites are later burial sites marked by large stones, mostly belonging to the Iron Age. C is wrong because Palaeolithic sites are far older hunting camps with rough unpolished tools and no sign of herding. Exam tip: remember Piklihal, Utnur, Maski, Brahmagiri and Sanganakallu together as the Deccan Neolithic ash-mound sites.

The correct answer is C, Chalukya - Tanjore. Tanjore, or Thanjavur, was the capital of the Cholas and not of the Chalukyas, so this pair is wrongly matched. The Chalukyas of Badami ruled from Badami, also called Vatapi, in present-day Bagalkot district of Karnataka, and their later branch ruled from Kalyani. Tanjore became famous under Rajaraja Chola I, who built the Brihadeeswara temple there around 1010 CE. A is correctly matched because the Gurjara-Pratiharas ruled from Kannauj, which they won in the long tripartite struggle against the Palas and the Rashtrakutas. B is correctly matched because Kanchi, or Kanchipuram, was the Pallava capital and their temple-building centre. D is correctly matched because the Sena rulers of Bengal had their capital at Lakhnauti, also known as Gauda. Exam tip: fix the pairs Badami with Chalukyas, Tanjore with Cholas, Kanchi with Pallavas and Madurai with Pandyas.

The correct answer is D, Kadambas. The Chalukyas of Badami began as feudatories of the Kadambas of Banavasi and broke away as the Kadamba power declined. Pulakeshin I, who ruled in the middle of the sixth century, made Badami, also called Vatapi, his fortified capital, performed the Ashvamedha sacrifice and is counted the first independent Chalukya ruler. The dynasty reached its height under Pulakeshin II, who defeated Harshavardhana on the Narmada and whose court poet Ravikirti wrote the Aihole inscription. A is wrong because the Hoysalas of Dwarasamudra rose much later, around the eleventh and twelfth centuries. B is wrong because the Pandyas of Madurai ruled the far south and were never overlords of Badami. C is wrong because the Pallavas of Kanchi were rivals, not masters, though Narasimhavarman I did sack Badami in 642 CE. Exam tip: link Kadambas of Banavasi to the rise of the Badami Chalukyas under Pulakeshin I.

The correct answer is A, 6. The Kyoto Protocol set its target on a basket of six greenhouse gases, to be cut by an average of 5.2 per cent below 1990 levels. The six are carbon dioxide, methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride. The protocol was adopted at Kyoto in Japan on 11 December 1997 under the UN Framework Convention on Climate Change and came into force on 16 February 2005; its first commitment period ran from 2008 to 2012 and bound the industrialised countries listed in Annex I. B, C and D are wrong because they overstate the basket: only six gases were covered in the first period, and nitrogen trifluoride was added as a seventh gas later, through the Doha Amendment for the second commitment period. Exam tip: fix the numbers together, six gases, 5.2 per cent, base year 1990 and the period 2008 to 2012.

The correct answer is C, Iodine. A shortage of iodine makes the thyroid gland in the neck swell, a condition called goitre. The thyroid needs iodine to make the hormone thyroxine, and when iodine is short the gland grows larger to trap whatever little is available, so the neck looks visibly swollen. Severe deficiency in children stunts growth and mental development, a condition called cretinism, which is why India fortifies common salt with iodine and runs the National Iodine Deficiency Disorders Control Programme. A is wrong because a lack of vitamin C causes scurvy, with bleeding gums and slow healing of wounds. B is wrong because a lack of vitamin D causes rickets in children and osteomalacia in adults, both bone diseases. D is wrong because a lack of calcium weakens bones and teeth and can cause muscle cramps, not a swollen neck. Exam tip: pair iodine with thyroxine and goitre, and remember iodised salt as the simple remedy.

The correct answer is A, 42 degrees Celsius. A clinical thermometer is marked from 35 to 42 degrees Celsius, which on the Fahrenheit scale is 94 to 108 degrees. The scale is kept short because human body temperature never strays far from the normal value of about 37 degrees Celsius, or 98.6 degrees Fahrenheit, and a narrow range lets the marks be spaced widely enough to read a change of one tenth of a degree. The mercury type has a kink, a narrow bend just above the bulb, which stops the mercury from running back so the reading can be taken after the thermometer is removed. B, C and D are wrong because temperatures of 44, 46 and 48 degrees Celsius lie far beyond what a living body can reach, so those markings would be wasted; a laboratory thermometer covering about minus 10 to 110 degrees Celsius is used for such higher readings. Exam tip: clinical 35 to 42 degrees Celsius, normal body temperature 37 degrees Celsius.

The correct answer is B, Water - 1200. Water has a specific heat capacity of about 4186 joule per kilogram per kelvin, not 1200, so this pair is the wrong one. Specific heat capacity is the heat needed to raise the temperature of one kilogram of a substance by one kelvin, and water's value is the highest among common liquids. That is why water is used as a coolant in car radiators and industry, why the sea warms and cools slowly, and why coastal places have a milder climate than inland towns. A is a correct pair because aluminium takes about 900 joule per kilogram per kelvin. C is a correct pair because carbon in its graphite form is close to 506.5. D is a correct pair because tungsten, a heavy metal, needs only about 134.4, so metals heat up quickly. Exam tip: remember water as about 4186 joule per kilogram per kelvin, which is one calorie per gram per degree Celsius.

The correct answer is D, 11 points. A blank document in MS Word 2016 opens with the body font Calibri at a size of 11 points. A point is a printing unit equal to one seventy-second of an inch, so size here means the height of the type, and the setting can be seen in the Font group of the Home tab. The default can be changed for good by opening the Font dialog box, choosing the font and size wanted and clicking Set As Default, which stores it in the Normal template. A is wrong because 12 points with Times New Roman was the default of the older Word 2003 and earlier versions. B is wrong because 14 points is a heading size a user must apply. C is wrong because 10 points is smaller than the default and again has to be set by hand. Exam tip: Word 2016 opens with Calibri 11 point, Word 2003 with Times New Roman 12 point.

The correct answer is C, Velocity and time. The first equation of motion is written as v equals u plus a t, so it tells how the velocity of a body changes with time. Here u is the initial velocity, v the velocity after time t and a the uniform acceleration. All three equations of motion hold only for straight-line motion with constant acceleration. A is wrong because the link between position and time is the second equation, s equals u t plus half a t squared. B is wrong because the link between position and velocity is the third equation, v squared equals u squared plus two a s, which has no time term. D is wrong because acceleration appears in all three equations but none of them connects velocity with acceleration alone; either time or displacement must come in. Exam tip: remember the three as velocity-time, position-time and velocity-position in that order.

The correct answer is A, Frequency. Pitch is how shrill or how flat a sound seems to the ear, and it is decided by frequency, the number of vibrations per second measured in hertz. A higher frequency gives a shriller sound, so a whistle or a woman's voice has a higher pitch than a drum or a man's voice; the human ear hears roughly 20 to 20000 hertz. B is wrong because wavelength changes with the medium the sound travels through, while the pitch a listener hears stays the same, so frequency and not wavelength fixes pitch. C is wrong because amplitude decides loudness, which is why striking a drum harder makes it louder but not shriller. D is wrong because timbre, or quality, is what lets us tell a flute from a violin playing the same note at the same loudness. Exam tip: frequency gives pitch, amplitude gives loudness and waveform gives quality.

The correct answer is B, In the same direction. In a class 3 lever the fulcrum is at one end, the effort is applied in the middle and the load sits at the far end. Since both the effort and the load lie on the same side of the fulcrum, the beam turns one way and they move in the same direction. The effort arm is shorter than the load arm, so the mechanical advantage is less than one and more effort is needed than the load; what such a lever gains is speed and a wider sweep of movement. The human forearm, a pair of sugar tongs, a fishing rod and a stapler work this way. A is wrong because effort and load move oppositely in a class 1 lever, where the fulcrum lies between them, as in a see-saw or scissors. C is wrong because a lever turns about a fixed point and its two ends never move at right angles to each other. D is wrong because the size of the load changes the force needed, not the direction of motion. Exam tip: class 1 has the fulcrum in the middle, class 2 the load, class 3 the effort.

The correct answer is D, Gustatory receptors. The receptors that pick up taste are called gustatory receptors, and they sit inside the taste buds on the tongue. They respond only to substances dissolved in saliva, which is why a dry tongue tastes little, and they report five basic tastes, sweet, sour, salty, bitter and umami. From the tongue the signal travels along cranial nerves to the brain, where taste and smell together give food its flavour. A is wrong because sensory receptor is the broad name for every receptor of the body, including those for light, sound, touch and pressure. B is wrong because chemoreceptor is the wider class that covers both taste and smell, so it does not name the taste receptor in particular. C is wrong because olfactory receptors lie in the lining of the nose and detect smell. Exam tip: gustatory means taste, olfactory means smell, auditory means hearing.

The correct answer is B, Class B. Fires are sorted into classes by what is burning, and a fire fed by flammable liquids such as petrol, diesel, kerosene, oil, paint or thinner is a class B fire. Such a fire is put out by smothering it with foam, carbon dioxide or dry chemical powder, which cuts off the oxygen. Water must never be thrown on burning oil, because the liquid floats on water and spreads the flames further. A is wrong because class D fires involve burning metals like magnesium, sodium and potassium, which need special dry powders. C is wrong because class C covers fires in live electrical equipment in common usage, and flammable gases under the Indian Standard. D is wrong because class A fires are the ordinary ones in solids like wood, paper and cloth, where water is the cheapest and best agent. Exam tip: A for solids, B for liquids, C for electrical or gas and D for metals.

The correct answer is A, The principle of conservation of energy is not violated. As the body falls its height shrinks, so the potential energy m g h falls, but exactly that much energy reappears as kinetic energy, half m v squared, because the body speeds up. The sum of the two stays the same at every point of the fall, so the total mechanical energy is conserved and energy is only changing form. At the moment of release the energy is all potential; just before the body strikes the ground it is almost all kinetic. When air resistance acts, the small shortfall leaves as heat and sound, so the energy is still accounted for. B is wrong because no energy is destroyed, only converted. C and D are wrong because gravity is a force, not a law that can be obeyed or broken, and neither statement answers what happens to the lost potential energy. Exam tip: for free fall, m g h plus half m v squared stays constant.

The correct answer is B, Static friction > Kinetic friction > Rolling friction. For the same pair of surfaces the order of friction is always static, then kinetic, then rolling. Static friction is the largest because the surfaces interlock while at rest and that grip has to be broken to start motion. Once sliding begins the contact keeps breaking and remaking, so kinetic friction is smaller. Rolling friction is the smallest of the three, since a rolling wheel does not slide over the road but only presses and deforms it slightly at the point of contact. This is exactly why wheels, rollers and ball bearings are used to shift heavy loads. A and D are wrong because they place rolling friction at the top, though it is the least of the three. C is wrong because it puts rolling friction above kinetic friction, reversing the true order. Exam tip: static greater than kinetic greater than rolling; the smallest of them gave us the wheel.

The correct answer is A, low coefficient of friction. Teflon is the trade name of polytetrafluoroethylene, a polymer whose surface is one of the most slippery among solids, with a coefficient of friction of about 0.04. A bearing has to let a shaft turn with as little rubbing as possible, so this slipperiness is the reason Teflon is chosen; it also lets many such bearings work without any oil or grease. The polymer was found by accident by Roy Plunkett in 1938, resists almost every chemical and holds up to about 260 degrees Celsius, which is why it also coats non-stick cookware and is wound as sealing tape on pipe threads. B is wrong because Teflon is a poor conductor of heat, so it is not chosen to carry heat away. C is wrong because saving space depends on the design of the bearing, not on the material. D is wrong because only the first reason holds. Exam tip: Teflon is PTFE, the non-stick polymer with the lowest friction.

The correct answer is A, Deposition. Deposition is the direct change of a substance from the gaseous state to the solid state, without passing through the liquid state in between. It is the exact reverse of sublimation. Frost forming on a cold window pane on a winter morning is deposition, because water vapour in the air turns straight into ice crystals. Iodine vapour and carbon dioxide behave the same way when they are cooled strongly. In such a change the particles lose energy, come very close together and settle into a fixed arrangement, so the substance gets a definite shape and volume. B is wrong because sublimation is the opposite change, a solid turning directly into a gas, as camphor and naphthalene balls do. C is wrong because vaporisation is a liquid changing into a gas. D is wrong because freezing is a liquid changing into a solid, as water does at 0 degree Celsius. Exam tip: remember the pair, sublimation is solid to gas and deposition is gas to solid.

The correct answer is C, respiration. In the equation given, glucose reacts with oxygen to release carbon dioxide, water and energy, and the breakdown of food inside the cell to release energy is called respiration. Oxygen is used here, so this is aerobic respiration, and it takes place in the mitochondria, which is why the mitochondrion is called the powerhouse of the cell. The energy released is stored in ATP. Without oxygen, muscle cells break glucose down only to lactic acid and yeast breaks it down to ethanol and carbon dioxide, and both of these release far less energy. A is wrong because metabolism is the whole set of chemical reactions going on in the body, of which respiration is only one. B is wrong because digestion merely breaks large food molecules into simpler ones such as glucose and does not release energy in this way. D is wrong because energy conversion is a loose general phrase, not the name of this reaction. Exam tip: glucose plus oxygen giving carbon dioxide, water and energy is aerobic respiration; without oxygen it gives lactic acid in muscles and ethanol in yeast.

The correct answer is D, Weight. The weight of an object is the force with which the earth attracts it, so the force of gravity acting on an object is its weight. Weight is calculated as W equals mg, where m is the mass of the body and g is the acceleration due to gravity, about 9.8 metre per second squared at the surface of the earth. Weight is a force, so it is a vector quantity and its SI unit is the newton. Because g changes from place to place, the same object weighs a little less at the equator than at the poles and about one sixth as much on the moon, while its mass stays exactly the same. A is wrong because impulse is force multiplied by the time for which it acts, and it changes the momentum of a body. B is wrong because mass is the quantity of matter in a body, a scalar measured in kilograms, which does not change with place. C is wrong because acceleration is the rate of change of velocity. Exam tip: mass in kilograms never changes, weight in newtons changes with g.

The correct answer is A, Pigeon. Birds and mammals are warm-blooded, which means they keep their body temperature nearly constant whatever the temperature outside, and a pigeon is a bird. Such animals are called homeothermic or endothermic; they produce the heat they need by oxidising food, which is why they eat more for their body size. Reptiles, amphibians and fishes are cold-blooded, or poikilothermic, so their body temperature rises and falls with the surroundings. That is why many of them bask in the sun to warm up and become inactive in the cold season. B is wrong because a crocodile is a reptile and therefore cold-blooded. C is wrong because a toad is an amphibian and also cold-blooded. D is wrong because the body temperature of a fish follows the temperature of the water around it. Exam tip: only birds and mammals are warm-blooded, so every reptile, amphibian and fish in an option list is cold-blooded.

The correct answer is B, +3. The object stands between the pole and the focus of the concave mirror, so the image formed is virtual, erect and enlarged, and the magnification is positive. Using the sign convention, u is -12 cm and f is -18 cm. From the mirror formula, 1/v + 1/u = 1/f, we get 1/v = 1/f - 1/u = -1/18 + 1/12 = 1/36, so v = +36 cm, an image formed 36 cm behind the mirror. Magnification m = -v/u = -36 divided by -12, which is +3, so the image is three times the size of the object. This is exactly why a concave mirror is used as a shaving mirror and by dentists. A is wrong because a negative magnification means a real and inverted image, which a concave mirror gives only when the object lies beyond the focus. C is wrong for the same reason. D is wrong because an image smaller than the object is never formed in this position. Exam tip: an object inside the focus of a concave mirror always gives a virtual, erect and magnified image.

The correct answer is D, Dilution. Adding water to an acid spreads the same number of hydrogen ions through a larger volume, so the number of hydrogen ions per unit volume falls, and that process is called dilution. A dilute acid therefore acts less strongly than a concentrated one, even though the acid itself is the same substance. Dilution of a strong acid is exothermic, so acid is always added slowly to water with constant stirring, never water to acid, or the heat released can make the mixture splash out. The same idea applies to bases, where dilution lowers the number of hydroxide ions per unit volume. A is wrong because concentration means increasing the amount of acid in a given volume, which is the opposite of what happens here. B is wrong because acidification means making a substance acidic, not thinning an acid that is already there. C is wrong because neutralisation is the reaction of an acid with a base to give a salt and water. Exam tip: always add acid to water, never water to acid.

The correct answer is C, Stomata. Stomata are the tiny pores on the surface of a leaf through which a plant takes in carbon dioxide and gives out oxygen and water vapour, so the exchange of gases takes place through them. Each stoma is bounded by two bean-shaped guard cells that swell to open the pore and shrink to close it, and this is how the plant controls its water loss. Most stomata lie on the lower surface of a leaf, so less water is lost to direct sunlight. Transpiration also happens largely through these pores. A is wrong because the cell membrane controls what enters and leaves a single cell, not the gas exchange of the whole plant. B is wrong because the nucleus carries the genetic material and directs the activities of the cell. D is wrong because guard cells only open and close the pore, while the exchange itself happens through the stomatal opening. Exam tip: stomata do the gas exchange and transpiration, guard cells only open and close them.

The correct answer is C, Ammonium chloride. Ammonium chloride is the salt of a strong acid, hydrochloric acid, and a weak base, ammonium hydroxide, so its aqueous solution is acidic and its pH is less than 7. When such a salt dissolves, the ion of the weak base hydrolyses in water and releases hydrogen ions, which is why the solution turns blue litmus red. The rule is simple: a strong acid with a weak base gives an acidic salt, a weak acid with a strong base gives a basic salt, and a strong acid with a strong base gives a neutral salt. A is wrong because sodium carbonate comes from a strong base and the weak carbonic acid, so its solution is basic with a pH above 7. B is wrong because sodium chloride comes from a strong acid and a strong base, so its solution is neutral with a pH of 7. D is wrong because sodium bicarbonate is also basic, which is why it serves as baking soda and as an antacid. Exam tip: the stronger parent decides, so strong acid plus weak base means an acidic salt.

The correct answer is C, Momentum. A quantity that has both magnitude and direction is a vector, and momentum, which is the product of mass and velocity, is a vector because velocity has a direction. Its SI unit is kilogram metre per second and its direction is the same as that of the velocity. Quantities that have magnitude alone are called scalars. Displacement, velocity, acceleration, force and weight are other common vectors, while mass, distance, speed, time, work, energy and temperature are scalars. Vectors are added by the triangle or parallelogram law and not by simple arithmetic, which is why two equal forces acting in opposite directions cancel each other. A is wrong because mass is a scalar, the quantity of matter in a body. B is wrong because distance is the total length of the path covered and has no direction; its vector counterpart is displacement. D is wrong because speed is a scalar and its vector counterpart is velocity. Exam tip: distance and speed are scalars, while displacement, velocity and momentum are vectors.

The correct answer is B, 540 cal. The heat produced by a current is given by Joule's law of heating, H equals I squared into R into t. Here the current is 0.3 A, the resistance is 418 ohms and the time is 1 minute, which is 60 seconds. So H = 0.09 into 418 into 60 = 2257.2 joule. One calorie equals 4.18 joule, so 2257.2 divided by 4.18 gives 540 calorie. Joule's law says the heat produced is proportional to the square of the current, to the resistance and to the time, which is why doubling the current gives four times the heat. The same law explains the electric iron, the heater, the geyser, the filament of a bulb and the fuse that melts to protect a circuit. A is wrong because 360 calorie would need a current of about 0.245 A for the same resistance and time. C is wrong because it is one tenth of the correct value. D is wrong because 36 calorie would need a current of only about 0.077 A. Exam tip: use H equals I squared Rt, then divide the joule figure by 4.18 to get calories.

The correct answer is C, neutralisation reaction. In the given equation sodium hydroxide, which is a base, reacts with sulphuric acid to give sodium sulphate and water, and a reaction in which an acid and a base cancel each other to form a salt and water is called neutralisation. Its general form is acid plus base gives salt plus water, and heat is given out, so the reaction is exothermic. Two molecules of sodium hydroxide are needed here because sulphuric acid is dibasic and supplies two hydrogen ions. Everyday examples are an antacid taken for acidity in the stomach, lime spread on an acidic soil and baking soda rubbed on a bee sting. A is wrong because a precipitation reaction forms an insoluble solid, while both products here stay in solution. B is wrong because in a decomposition reaction a single compound splits into two or more simpler substances. D is wrong because a redox reaction involves a change in oxidation numbers, and here they do not change. Exam tip: acid plus base giving salt and water is always neutralisation.

The correct answer is D, 11.36%. Mass by mass percentage of a solution is the mass of the solute divided by the mass of the whole solution, multiplied by 100. The solute here is 41 g of common salt and the solvent is 320 g of water, so the mass of the solution is 41 plus 320, that is 361 g. The concentration is therefore 41 divided by 361, multiplied by 100, which gives 11.36 per cent. The common mistake is to divide by the mass of the solvent alone instead of the solution; 41 divided by 320 into 100 gives 12.81 per cent, which is not even an option. A is wrong because 12.36 per cent would need about 45 g of salt in the same solution. B is wrong because 9.35 per cent would need about 34 g of salt. C is wrong because 10.36 per cent would need about 37 g of salt. Exam tip: mass percentage always uses solute divided by solute plus solvent, never solute divided by solvent.

The correct answer is A, 318 K. A reading of 113 on the Fahrenheit scale works out to 45 degrees Celsius, and adding 273 to that gives about 318 K. Fahrenheit is turned into Celsius with the relation C = (F - 32) x 5/9, so (113 - 32) x 5/9 = 81 x 5/9 = 45 degrees Celsius. The Kelvin scale begins at absolute zero and its degree is the same size as the Celsius degree, so K = C + 273.15, which makes 45 degrees Celsius equal to 318.15 K, written as 318 K in the options. Keep in mind that 0 degrees Celsius is 273 K, and that water freezes at 32 F and boils at 212 F. B is wrong because 45 is the Celsius value and not the Kelvin value. C is wrong because that figure comes from an incomplete conversion instead of the full formula. D is wrong because it adds 273 to the wrong Celsius value. Exam tip: do it in two steps, Fahrenheit to Celsius first, then add 273.

The correct answer is D, Ghana. Kwame Nkrumah led Ghana and was one of the five founders of the Non-Aligned Movement. He took Ghana to independence in 1957, the first country in sub-Saharan Africa to break free of colonial rule, and served first as its Prime Minister and then as its President. The Non-Aligned Movement was built by five leaders, Jawaharlal Nehru of India, Gamal Abdel Nasser of Egypt, Josip Broz Tito of Yugoslavia, Sukarno of Indonesia and Nkrumah of Ghana, who refused to join either the American or the Soviet bloc during the Cold War. Their effort led to the first NAM summit at Belgrade in 1961. A is wrong because Nigeria became independent in 1960 and its early leader was Abubakar Tafawa Balewa. B is wrong because Kenya was led to freedom by Jomo Kenyatta. C is wrong because the first Prime Minister of Uganda was Milton Obote. Exam tip: remember the five founders of NAM and the Belgrade summit of 1961.

The correct answer is C, 2 s. A simple pendulum about one metre long completes one full swing in roughly two seconds, and a pendulum of this length is called the seconds pendulum. The time period of a simple pendulum is T = 2 pi times the square root of L divided by g, where L is the length of the thread and g is the acceleration due to gravity, about 9.8 metres per second squared. Putting L = 1 metre gives T = 2 x 3.14 x the square root of 1 divided by 9.8, which comes to about 2.01 seconds. The period depends only on the length and on g, not on the mass of the bob or on how far it is pulled aside, so long as the swing is small. A is wrong because a 6 second period needs a thread about 9 metres long. B is wrong because a 4 second period needs a thread about 4 metres long. D is wrong because a 1 second period belongs to a thread of only about 25 centimetres. Exam tip: the period doubles only when the length becomes four times.