UPSC 2021 Previous Year GK Questions with Answers

The correct answer is D, Methanol. No pathway of respiration in living cells turns glucose into methanol.

Glucose is first split in the cytoplasm into two molecules of pyruvate; this step, glycolysis, is common to all cells. What follows depends on oxygen. With oxygen, pyruvate is broken down in the mitochondria to carbon dioxide and water, releasing the most energy. Without oxygen, yeast converts pyruvate to ethanol and carbon dioxide, the basis of brewing and bread making, while our muscle cells during hard exercise convert it to lactic acid, which causes cramps.

A is wrong: ethanol is the product of anaerobic respiration (fermentation) in yeast.

B is wrong: lactic acid forms in muscle cells and in lactic acid bacteria when oxygen is short.

C is wrong: water, with carbon dioxide, is the end product of aerobic respiration.

Exam tip: glucose → pyruvate (cytoplasm) → CO2 + H2O (with oxygen), ethanol + CO2 (yeast), lactic acid (muscle).

The correct answer is C, HIV-AIDS. HIV spreads through body fluids such as blood, semen, vaginal fluid and breast milk, not through droplets from coughing, sneezing or talking.

The human immunodeficiency virus attacks helper T cells and weakens the immune system; AIDS is its late stage. It passes on through unprotected sexual contact, transfusion of infected blood, shared needles and syringes, and from an infected mother to her child during pregnancy, birth or breastfeeding. It does not spread by shaking hands, sharing food, hugging or breathing the same air.

A is wrong: the bacteria and viruses that cause pneumonia spread through droplets from the nose and mouth.

B is wrong: COVID-19, caused by the SARS-CoV-2 virus, spreads mainly by respiratory droplets and aerosols.

D is wrong: tuberculosis, caused by Mycobacterium tuberculosis, spreads when a patient with lung TB coughs or sneezes.

Exam tip: droplet diseases = TB, COVID-19, flu, pneumonia, common cold; HIV and hepatitis B = blood and body fluids.

The correct answer is C, Smooth muscle. Smooth muscle is a muscular tissue, one of the four basic animal tissues, not a connective tissue.

Animal tissues are of four kinds: epithelial, connective, muscular and nervous. Connective tissues have cells spread in a matrix and bind or support other parts; they include bone, cartilage, blood, areolar tissue, adipose tissue, ligaments and tendons. Smooth muscle is made of spindle-shaped, unstriated cells that contract on their own, without our will, in the walls of the stomach, intestines, blood vessels and the iris.

A is wrong: a ligament is dense connective tissue joining bone to bone; it is strong and elastic.

B is wrong: a tendon is dense connective tissue joining muscle to bone; it is strong but has little elasticity.

D is wrong: cartilage is a connective tissue with a firm matrix, found in the nose, ear, trachea and joint surfaces.

Exam tip: ligament = bone to bone, tendon = muscle to bone; muscles (smooth, skeletal, cardiac) are a separate tissue.

The correct answer is D, Aerenchyma. Aerenchyma is a kind of parenchyma whose cells enclose large air-filled spaces.

These air cavities keep aquatic plants such as water hyacinth, lotus and Hydrilla afloat and let oxygen move down to roots and stems that sit in waterlogged soil or under water. Rice and many marsh plants also form aerenchyma in their roots when the soil is flooded. The name itself helps: 'aer' means air and 'enchyma' means tissue.

A is wrong: sclerenchyma has thick, lignified walls and dead cells packed close together; it gives hardness, as in coconut husk.

B is wrong: meristem cells are small, living, dividing cells packed without intercellular spaces.

C is wrong: collenchyma has living cells thickened at the corners with very little space between them; it gives flexibility to stems and leaf stalks.

Exam tip: aerenchyma = air spaces and buoyancy in water plants; sclerenchyma = hardness; collenchyma = flexibility.

The correct answer is C, Cell wall. Animal cells are bounded only by a flexible cell membrane; a rigid cell wall is found in plants, fungi and bacteria.

In plant cells the cell wall lies outside the cell membrane and is made mainly of cellulose; it gives shape, strength and protection against bursting when the cell takes in water. Fungi have walls of chitin and bacteria of peptidoglycan. Animal cells lack it, which lets them change shape, move and form tissues such as muscle. Other structures usually absent from animal cells are chloroplasts and a large central vacuole, while centrioles are typical of animal cells.

A is wrong: the cell membrane (plasma membrane) surrounds every living cell, animal or plant.

B is wrong: the endoplasmic reticulum, which makes proteins and lipids, is present in animal cells.

D is wrong: lysosomes, the digestive bags called suicide bags of the cell, are characteristic of animal cells.

Exam tip: plant cell = cell wall, chloroplast, large vacuole; animal cell = centrioles and lysosomes, no cell wall.

The correct answer is B. A short-sighted (myopic) person sees near things clearly but distant things blurred, and a concave lens corrects it.

In myopia the eyeball is too long or the eye lens too strongly curved, so light from a distant object comes to a focus in front of the retina instead of on it. The far point of the eye moves closer than infinity. A concave (diverging) lens of suitable power spreads the incoming rays slightly, so they focus exactly on the retina. Its power is negative, measured in dioptres.

A is wrong: blurred near vision with clear distant vision is long-sightedness (hypermetropia), and both the defect and the lens are mismatched here.

C is wrong: it describes hypermetropia but pairs it with a concave lens.

D is wrong: the symptoms are right for myopia, but a convex lens would make it worse.

Exam tip: myopia = near clear, far blurred, concave lens; hypermetropia = far clear, near blurred, convex lens; presbyopia = age, often bifocals.

The correct answer is A, 5 cm, converging. A real, inverted image of the same size forms only when the object sits at twice the focal length of a convex lens, so 2f = 10 cm and f = 5 cm.

For a convex (converging) lens, an object placed at 2F gives a real, inverted image of equal size at 2F on the other side. Check with the lens formula 1/v − 1/u = 1/f: with u = −10 cm and v = +10 cm, 1/f = 1/10 + 1/10 = 1/5, so f = +5 cm. A positive focal length confirms a converging lens. Magnification m = v/u = −1, which means same size and inverted.

B is wrong: a diverging (concave) lens always forms a virtual, erect and diminished image, never a real one.

C is wrong: with f = 20 cm the object at 10 cm would be inside the focus and the image would be virtual and enlarged.

D is wrong: a concave lens cannot form a real image, whatever its focal length.

Exam tip: convex lens, object at 2F gives image at 2F, real, inverted and the same size; u = v = 2f.

The correct answer is C, Infrared and microwave radiations. Both kinds of radiation carry energy that food absorbs as heat, and both are used in everyday kitchens.

Infrared radiation is the heat radiation given out by hot bodies: a grill, a toaster, an oven element or glowing coals cook the surface of food mainly by infrared rays. A microwave oven uses microwaves of about 2.45 GHz; water molecules in the food are polar, so they keep turning with the oscillating field and the friction heats the food from within. So two different bands of the spectrum are put to use in cooking.

A is wrong: infrared is used, but it leaves out the microwave oven.

B is wrong: microwaves are used, but grills and toasters cook with infrared.

D is wrong: X-rays, gamma rays and ultraviolet are harmful ionising or high-energy radiations and radio waves carry too little energy; none of them is used to cook.

Exam tip: microwave oven = about 2.45 GHz, heats water molecules; grill and toaster = infrared.

The correct answer is D, 1, 2 and 3. Indian bond yields respond to the RBI's policy, to domestic inflation and short-term rates, and also to the US Federal Reserve through global capital flows.

A bond's yield is the return an investor earns on it, and it moves opposite to the bond's price. When the RBI cuts the repo rate or buys government securities through open market operations, yields tend to fall; tightening pushes them up. Higher inflation makes investors demand a higher return, and short-term rates set the base from which longer yields are priced. When the US Federal Reserve raises rates, foreign investors may pull money out of Indian bonds for safer US assets, which lowers bond prices in India and lifts yields.

A is wrong because inflation and short-term rates also matter.

B is wrong because the RBI is only one of several influences.

C is wrong because both central banks also move yields.

Exam tip: bond price and yield move in opposite directions; inflation up, yields up.

The correct answer is B, 2 and 3 only. Urban Cooperative Banks are regulated by the RBI, not by local boards, and they may raise capital through equity and preference shares.

Statement 1 is wrong: UCBs are registered under State or Multi-State Cooperative Societies Acts, but their banking functions are regulated and supervised by the Reserve Bank of India; no local boards of State Governments do this. Statement 2 is correct: the Banking Regulation (Amendment) Act, 2020 lets cooperative banks, with RBI approval, issue equity shares, preference shares and other securities to raise capital. Statement 3 is correct: cooperative banks were brought under the Banking Regulation Act, 1949 from 1 March 1966, through an amendment applying the Act to cooperative societies.

A is wrong because statement 1 is false.

C is wrong because it keeps the false statement 1 and drops the true statement 2.

D is wrong because statement 1 is incorrect.

Exam tip: cooperative banks came under the BR Act in 1966; the 2020 amendment strengthened RBI control over them.

The correct answer is A, 1 and 4 only. A dearer substitute pushes buyers towards this good, and a fall in its own price leads them to buy more of it.

Statement 1 is correct: if tea becomes costlier, people buy more coffee, so demand for coffee rises. Statement 4 is correct: by the law of demand, a lower price raises the quantity buyers want. Statement 2 is wrong: if the price of a complement rises (petrol for cars), demand for the good falls. Statement 3 is wrong: for an inferior good, demand falls when income rises, because consumers shift to better goods.

B is wrong because it includes statements 2 and 3, both of which reduce demand.

C is wrong because statement 3 describes a fall, not a rise, in demand for an inferior good.

D is wrong because it includes 2 and 3 and leaves out 4, the plainest case of the law of demand.

Exam tip: substitute price up, demand up; complement price up, demand down; inferior good, income up, demand down.

The correct answer is A, Nizam Shahis : Bijapur, which is the mismatched pair. The Nizam Shahis ruled from Ahmadnagar, founded by Malik Ahmad in 1490, while Bijapur belonged to the Adil Shahis of Yusuf Adil Shah. All five Deccan Sultanates grew out of the break-up of the Bahmani kingdom between about 1490 and 1518, and four of them joined hands to crush Vijayanagara at the battle of Talikota in 1565. Bijapur is remembered for the Gol Gumbaz, Golconda for its fort and diamonds, and Ahmadnagar for Chand Bibi’s defence against the Mughals. Option B is a correct pair, because the Barid Shahis held Bidar, the last Bahmani capital. Option C is a correct pair, because the Qutb Shahis of Quli Qutb Shah ruled Golconda and later founded Hyderabad. Option D is a correct pair, because the Imad Shahis held Berar, the first province to break away and the first to be annexed by Ahmadnagar. Exam tip: Ahmadnagar Nizam Shahi, Bijapur Adil Shahi, Golconda Qutb Shahi, Bidar Barid Shahi, Berar Imad Shahi.

The correct answer is C, Kolkata. The Kolkata port, now named Syama Prasad Mookerjee Port, stands on the Hooghly river about 200 kilometres inland from the Bay of Bengal, which makes it the only riverine major port in the country. Opened in 1870, it is also the oldest operating major port in India and serves a vast hinterland covering eastern India, Nepal and Bhutan. Its handicap is the silt the Hooghly carries: the channel must be dredged all the time, and because large modern ships still cannot reach the city, the Haldia Dock Complex was built downstream to take them. Option A is wrong because Mormugao in Goa is a coastal natural harbour at the mouth of the Zuari, famous for iron ore exports. Option B is wrong because Deendayal port, formerly Kandla, is a tidal sea port in the Gulf of Kachchh in Gujarat. Option D is wrong because Paradip in Odisha is an artificial deep water sea port on the coast. Exam tip: Kolkata is the only riverine major port, on the Hooghly, with Haldia as its deep water partner.

The correct answer is D, Chin Khilich Khan. Chin Qilich Khan, better remembered by his title Nizam-ul-Mulk Asaf Jah, was a Mughal noble appointed governor of the Deccan by Muhammad Shah. Tired of court intrigue at Delhi, he returned to the south, defeated his rival Mubariz Khan at Shakar Kheda in 1724 and from then on ruled the Deccan as an independent prince in all but name, founding the Asaf Jahi or Nizam dynasty of Hyderabad that lasted until 1948. He kept the forms of Mughal loyalty, struck coins in the emperor’s name, yet appointed his own officers and made war and peace on his own. Option A is wrong because Asaf Jah II, that is Nizam Ali Khan, was a later ruler of the same line, not its founder. Option B is wrong because Bahadur Shah was the Mughal emperor who ruled from 1707 to 1712. Option C is wrong because Alivardi Khan made himself independent in Bengal, not Hyderabad. Exam tip: Hyderabad 1724 Chin Qilich Khan, Awadh 1722 Saadat Khan, Bengal Murshid Quli Khan.

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 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 B, Abhaya Mudra. Early Mathura Buddhas show the right hand raised with the palm facing out, the gesture that says "fear not". The Mathura School flourished under the Kushanas in the first centuries CE, at the same time as the Gandhara school of the north-west. Mathura sculptors worked in the local spotted red sandstone and gave the Buddha a round smiling face, a shaven head with a spiral top-knot and a strong, fleshy body, a style that was wholly Indian. The seated Buddha from the Katra mound, now in the Mathura Museum, is a well-known example with the right hand in abhaya. Option A is wrong because the dhyana mudra of meditation, with hands resting in the lap, is typical of Gandhara images. Option C is wrong because the dharmachakra mudra of teaching became famous later, as in the Gupta-period Buddha of Sarnath. Option D is wrong because the varada mudra of giving, with the palm lowered, is seen more often in later images. Exam tip: Mathura means red sandstone and abhaya; Gandhara means grey schist and dhyana.

The correct answer is C, Anabaena. Anabaena is a cyanobacterium, a prokaryote with no true nucleus, and all prokaryotes are placed in Monera. In R.H. Whittaker's five-kingdom classification (1969), Monera holds the bacteria and the cyanobacteria, or blue-green algae, whose cells have no nuclear membrane and no membrane-bound organelles. Anabaena grows as chains of cells and has special thick-walled cells called heterocysts that fix nitrogen from the air. It lives inside the small water fern Azolla, which is why Azolla is used as a biofertiliser in paddy fields. Option A is wrong because diatoms are single-celled eukaryotes with glass-like silica walls, placed in Protista; their deposits form diatomaceous earth. Option B is wrong because Euglena is a protist that makes its own food in light but feeds like an animal in the dark. Option D is wrong because Ulothrix is a filamentous green alga with a true nucleus, grouped with plants. Exam tip: no true nucleus means Monera; Anabaena and Nostoc are the nitrogen-fixing cyanobacteria to remember.

The correct answer is C, Nitrogen. Nitrogen is an unreactive gas, so it drives the oxygen out of the packet and stops the oil in the chips from getting oxidised. Rancidity is the oxidation of fats and oils in food, which spoils their smell and taste. Chips are fried in oil, so they turn rancid quickly once they meet air. Filling the pack with nitrogen keeps oxygen out and also acts as a cushion that stops the chips from breaking in transport. Other ways to slow rancidity are adding antioxidants, storing food in airtight containers and keeping it in a refrigerator. Option A is wrong because carbon dioxide is used for fizzy drinks and some other foods, but the standard gas for chips is nitrogen, which is cheap and very unreactive. Option B is wrong because hydrogen is highly inflammable and unsafe inside food packs. Option D is wrong because oxygen is the very gas that causes rancidity in the first place. Exam tip: rancidity is oxidation of fats; nitrogen flushing and antioxidants prevent it.

The correct answer is C, minimum support price. The MSP is announced before sowing so that farmers know the lowest price at which the government will buy their crop. The Union Government fixes it on the recommendation of the Commission for Agricultural Costs and Prices (CACP), set up in 1965, and the final approval comes from the Cabinet Committee on Economic Affairs. It is announced separately for kharif and rabi crops, while sugarcane gets a fair and remunerative price instead. Wheat was the first crop brought under MSP, in 1966-67, at the start of the Green Revolution. Option A is wrong because a buffer stock is grain the government holds for food security, and no "buffer price" is announced for farmers. Option B is wrong because the issue price is the rate at which the Food Corporation of India sells grain to the States for the public distribution system. Option D is wrong because "fair sustenance price" is not an official price at all. Exam tip: MSP is recommended by the CACP and approved by the CCEA; sugarcane gets the FRP instead.