UPSC Civil Services 2024 Previous Year GK Questions with Answers

The correct answer is D, 1, 2 and 3. All three statements are correct about PFAS, the so-called 'forever chemicals'.

PFAS are a large family of man-made chemicals built on very strong carbon-fluorine bonds. They resist water, grease and heat, so they are used in non-stick cookware, water-proof clothing, grease-proof food packaging and fire-fighting foams. Because the carbon-fluorine bond is so hard to break, PFAS hardly degrade in nature and have spread into soil, groundwater, drinking water and food. They build up in the blood and organs of animals and humans over time, and long exposure has been linked to liver damage, weaker immunity and some cancers.

A is wrong: it leaves out statement 3, which is also true.

B is wrong: it leaves out statement 1, which is also true.

C is wrong: it leaves out statement 2, the very reason they are called forever chemicals.

Exam tip: PFAS = 'forever chemicals', carbon-fluorine bonds, non-stick and water-proof products, persistent and bioaccumulative.

The correct answer is B, Congo Basin. The Cuvette Centrale peatland of the Congo Basin is the world's largest tropical peatland.

Scientists mapped this vast peat swamp only in 2017, spread across the Republic of the Congo and the Democratic Republic of the Congo. It covers about 1.45 lakh square kilometres and stores roughly 29 billion tonnes of carbon, about three years of the world's fossil-fuel emissions. Peat forms when waterlogged plant matter does not fully decay, so draining it for farming, logging or oil drilling would release this carbon and worsen climate change.

A is wrong: the Amazon has peatlands too, but the largest single tropical peatland is in the Congo Basin.

C is wrong: the Kikori Basin in Papua New Guinea is a much smaller rainforest river basin.

D is wrong: the Rio de la Plata Basin in South America is mostly grassland, wetland and farmland, not the largest peatland.

Exam tip: Cuvette Centrale, Congo Basin = largest tropical peatland, about 29 billion tonnes of carbon.

The correct answer is C, Both 1 and 2. The Coriolis force grows with the speed of the wind and with latitude, so it is strongest at the poles and zero at the equator.

The Coriolis force is an apparent force caused by the Earth's rotation. It deflects moving air and water to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. Its strength is proportional to the speed of the moving body and to the sine of the latitude. At the equator the sine of zero degrees is zero, so there is no deflection, while at the poles it reaches its maximum. Because of this, tropical cyclones do not form within about 5 degrees of the equator, where the force is too weak to set up the spinning motion. It also explains why winds blow parallel to the isobars in the upper air, as geostrophic winds.

A is wrong: it leaves out statement 2, which is also correct.

B is wrong: it leaves out statement 1.

D is wrong: both statements are correct.

Exam tip: Coriolis force depends on wind speed and latitude; zero at the equator, maximum at the poles; right in the north, left in the south.

The correct answer is D, Marine West coast climate. Mild temperatures with small ranges, rain in every month and a total of about 50 to 250 cm describe the west coast marine (Cfb) type.

This climate is found on the western margins of continents in the middle latitudes, roughly 40 to 60 degrees, as in north-western Europe, British Columbia, southern Chile, Tasmania and New Zealand. Prevailing westerlies blow in from the ocean all year, bringing frequent cyclonic rain and keeping summers cool and winters mild, so both the annual and daily ranges stay small. Warm ocean currents such as the North Atlantic Drift add to the mildness.

A is wrong: the equatorial climate has heavy rain, usually above 200 cm, and its daily range is greater than its small annual range.

B is wrong: the China type has hot summers and cool winters, so its annual range is large, with rain peaking in summer.

C is wrong: humid subtropical is another name for the China type, with the same large summer-winter contrast.

Exam tip: marine west coast = British type, Cfb, westerlies, rain all year, mild winters and cool summers.

The correct answer is A, 1 only. Water vapour thins out quickly with height, but it is most plentiful in the warm tropics, not at the poles.

Water vapour is a variable gas of the atmosphere, making up anything from almost nil to about 4% of the air by volume. It enters the air by evaporation and transpiration, and warm air can hold far more of it than cold air. That is why about 90% of it stays in the lowest few kilometres of the troposphere and its share falls steadily with altitude. For the same reason it is highest in warm, humid equatorial regions, where it can reach 4%, and lowest over the cold poles and dry deserts, where it may be below 1%. It absorbs heat from the Earth and so helps keep the planet warm.

B is wrong: the poles are cold and hold the least water vapour.

C is wrong: it includes the false statement 2.

D is wrong: statement 1 is correct.

Exam tip: water vapour is up to 4% in warm, wet tropics and under 1% in cold or dry areas; it decreases with altitude.

The correct answer is B, Only two. Rows 3 and 4 are correct; rows 1 and 2 have the wrong region or type.

Fold mountains form when plates converge and layers of rock crumple. The Appalachians of eastern North America are old fold mountains raised in the Palaeozoic era and since worn down, and the Andes of South America are young fold mountains formed where the Nazca plate dives beneath the South American plate, so rows 3 and 4 are right. Block mountains form when a block of land is raised between faults; the Vosges in France and the Black Forest in Germany are classic examples, standing on either side of the Rhine rift valley. So row 1 is wrong, as the Vosges are in Europe and are block mountains. Row 2 is wrong because the Alps are young fold mountains, like the Himalayas.

A is wrong: two rows, not one, are correct.

C is wrong: only rows 3 and 4 are correct.

D is wrong: rows 1 and 2 contain errors.

Exam tip: block mountains = Vosges and Black Forest (Rhine rift); young fold = Alps, Himalayas, Andes, Rockies; old fold = Appalachians, Aravallis, Urals.

The correct answer is A, Only one. Only row 2 is fully correct; rows 1 and 3 each have a wrong entry.

Hundru Falls, near Ranchi in Jharkhand, is formed where the Subarnarekha river drops off the edge of the Ranchi plateau, part of the Chota Nagpur region, so row 2 is right. Dhuandhar Falls is on the Narmada at Bhedaghat near Jabalpur, where the river plunges into the marble gorge; Jabalpur lies in the Mahakoshal region between the Vindhya and Satpura ranges, not on the Malwa plateau, so row 1 fails on the region. Gersoppa Falls, better known as Jog Falls, is in the Western Ghats of Shivamogga district, Karnataka, but it is formed by the Sharavathi river, not the Netravati, so row 3 fails on the river.

B is wrong: only one row, not two, is correct.

C is wrong: rows 1 and 3 contain errors.

D is wrong: row 2 is correctly matched.

Exam tip: Jog/Gersoppa = Sharavathi; Dhuandhar = Narmada at Bhedaghat, Jabalpur; Hundru = Subarnarekha, Ranchi.

The correct answer is B, Gomati - Ghaghara - Gandak - Kosi. Below Prayagraj the Ganga receives the Gomati first, then the Ghaghara, then the Gandak and finally the Kosi as it flows east.

The Gomati, which rises near Pilibhit and flows past Lucknow and Jaunpur, joins the Ganga near Kaithi in Ghazipur district of Uttar Pradesh. The Ghaghara, coming down from Nepal as the Karnali, meets the Ganga near Chhapra in Bihar. The Gandak, known as the Narayani in Nepal, joins at Sonpur opposite Patna. The Kosi, the "Sorrow of Bihar" famous for shifting its course, joins near Kursela in Katihar district, close to the border with Jharkhand and West Bengal.

A is wrong: it puts the Ghaghara before the Gomati, but the Gomati joins further west.

C is wrong: it puts the Ghaghara first and the Kosi before the Gandak.

D is wrong: the Gandak joins near Patna, well west of the Kosi confluence at Kursela.

Exam tip: left-bank order below Prayagraj = Gomati (Ghazipur), Ghaghara (Chhapra), Gandak (Sonpur-Patna), Kosi (Kursela).

The correct answer is C, Côte d'Ivoire and Ghana. These two neighbouring West African countries grow well over half of the world's cocoa.

Cocoa is a tropical tree crop that needs heavy, well-spread rainfall, high humidity, temperatures of about 21 to 32 °C and shade, which is why it grows best within about 10 degrees of the Equator. The humid forest belt along the Gulf of Guinea offers exactly these conditions, and Côte d'Ivoire (Ivory Coast) ranks first and Ghana second in world output. In India cocoa is grown mainly in Kerala, Karnataka, Andhra Pradesh and Tamil Nadu, often as an intercrop with arecanut and coconut.

A is wrong: Algeria and Morocco lie in dry North Africa, where cocoa cannot grow.

B is wrong: Botswana and Namibia are arid southern African countries known for diamonds and minerals.

D is wrong: Madagascar is famous for vanilla and Mozambique for cashew, not for leading cocoa output.

Exam tip: cocoa = Gulf of Guinea; Côte d'Ivoire first, Ghana second.

The correct answer is A, 1 only. In January the northern oceans are warmer than the frozen continents, so isotherms bend north over the sea and south over the land; the Gulf Stream and North Atlantic Drift are warm currents, not cold ones.

Isotherms are lines joining places of equal temperature. In the northern hemisphere winter, land loses heat quickly and becomes very cold, while the ocean keeps its warmth. A given temperature is therefore found further north over the ocean and further south over the continents such as Siberia, which makes the lines bend. Statement 2 is wrong: the Gulf Stream and the North Atlantic Drift carry warm tropical water into the North Atlantic, making it warmer, and that warmth is why the isotherms bend sharply north there, keeping ports of north-west Europe ice-free.

B is wrong because statement 2 calls warm currents cold.

C is wrong because statement 2 is false.

D is wrong because statement 1 is a correct inference.

Exam tip: January isotherms bend poleward over oceans and equatorward over land; Gulf Stream and North Atlantic Drift are warm currents.

The correct answer is D, All four. A volcanic eruption throws out solid fragments, fine ash and dust, and a mixture of gases that includes nitrogen and sulphur compounds.

Material released by a volcano is of three kinds. Solid matter includes pyroclastic debris, the broken pieces of rock and lava blown out by the explosion, ranging from large volcanic bombs to small lapilli, along with fine ash and dust that can spread across continents. Liquid matter is the lava. Gases are mostly water vapour, followed by carbon dioxide, sulphur compounds such as sulphur dioxide and hydrogen sulphide, and nitrogen compounds, with smaller amounts of chlorine, hydrogen and argon. Sulphur dioxide forms sulphate aerosols in the stratosphere that can cool the climate for a year or two.

A is wrong because more than one item is a volcanic product.

B is wrong because the gases, not only the solids, come from eruptions.

C is wrong because none of the four can be left out.

Exam tip: volcanic gases = mostly water vapour, then carbon dioxide, sulphur and nitrogen compounds.

The correct answer is A, both statements are correct and Statement-II explains Statement-I. The troposphere is thickest over the equator because strong convection there carries heat high into the air.

The troposphere, the lowest layer of the atmosphere where almost all weather occurs, is about 18 km thick at the equator but only about 8 km at the poles. Intense heating of the surface near the equator sets up powerful rising convection currents, which lift warm air and moisture to great heights and push the top of the layer, the tropopause, upward. Over the cold poles convection is weak, so the layer stays shallow. Temperature in the troposphere falls by about 6.5 °C per kilometre of height.

B is wrong because convection is exactly the reason for the greater thickness.

C is wrong because Statement-II is correct.

D is wrong because Statement-I is correct.

Exam tip: troposphere about 18 km at the equator, about 8 km at the poles, because of convection.

The correct answer is D, Statement-I is incorrect, but Statement-II is correct. The atmosphere is heated mainly from below, by the Earth's own long wave (terrestrial) radiation, not directly by sunlight.

Incoming solar radiation is short wave, and the atmosphere is largely transparent to it, so most of it passes through and heats the Earth's surface. The warmed surface then gives off heat as long wave infrared radiation. Water vapour, carbon dioxide and other greenhouse gases absorb this long wave radiation well, and this is what warms the lower atmosphere. That is also why temperature normally falls with height in the troposphere.

A and B are wrong because Statement-I itself is false, so neither can be the answer.

C is wrong because it reverses the truth: Statement-I is the incorrect one, while Statement-II correctly describes greenhouse gases.

Exam tip: Sun gives short wave radiation that heats the ground; the ground gives long wave radiation that heats the air.

The correct answer is A, Fig. Each fig species is pollinated only by its own tiny fig wasp, and the two have evolved together over millions of years. A fig 'fruit' is really a closed bulb, the syconium, with hundreds of small flowers inside. A female wasp squeezes in through a tiny opening, pollinates the flowers and lays her eggs in some of them. The young wasps grow inside, mate, and the new females fly out carrying pollen to another fig. Without the wasp the fig cannot set seed, and without the fig the wasp cannot breed; this is obligate mutualism. Figs such as the banyan and peepal are keystone species, because their fruit feeds many birds and mammals through the year. Option B is wrong because mahua flowers are pollinated mainly by bats and some birds. Option C is wrong because sandalwood, a root hemiparasite, is visited by many kinds of insects, not one. Option D is wrong because silk cotton (semal) is pollinated mainly by birds. Exam tip: fig and fig wasp are the classic example of co-evolution and obligate mutualism.

The correct answer is D, the average number of live births a woman would have by the end of her child-bearing age. Total fertility rate (TFR) adds up the age-specific fertility rates of women aged 15 to 49 to show how many children a woman would have if she lived through these years at current rates. A TFR of about 2.1 is called the replacement level, because at that rate each generation just replaces itself; the extra 0.1 allows for deaths in childhood. TFR guides India's population policy and is measured by surveys such as the National Family Health Survey and the Sample Registration System. Option A is wrong because the number of births per 1,000 people in a year is the crude birth rate. Option B is wrong because TFR is counted per woman, not per couple, and uses current age-wise rates. Option C is wrong because birth rate minus death rate gives the natural growth rate of population. Exam tip: TFR is per woman, ages 15 to 49, with replacement level 2.1.

The correct answer is A, Canada and the United States of America. Their boundary, about 8,891 km long including the Alaska section, is the longest border between any two countries. It has two parts: about 6,400 km along the southern edge of Canada, much of it along the 49th parallel west of the Great Lakes and through the lakes themselves, and about 2,475 km between Alaska and Canada's Yukon and British Columbia. It is often called the world's longest undefended border and is looked after by the International Boundary Commission. Option D is wrong, though close: the Kazakhstan–Russia border, about 7,600 km, is the longest continuous land border. Option B is wrong because the Chile–Argentina border along the Andes, about 5,300 km, comes third. Option C is wrong because the China–India border is about 3,488 km. Exam tip: Canada–USA is the longest overall, Kazakhstan–Russia the longest continuous land border; India's longest border is with Bangladesh, 4,096 km.

The correct answer is B, 2 and 3 only. Shakyamuni and Tathagata are titles of the Buddha, while Nayaputta is a name of Mahavira. Shakyamuni means 'the sage of the Shakyas', the clan of Kapilavastu into which Siddhartha was born. Tathagata means 'the one who has thus gone', and the Buddha used it for himself in the Pali texts. Nayaputta (Nataputta) means 'son of the Naya or Jnatrika clan', and Buddhist texts call Mahavira Nigantha Nataputta. Option A is wrong because Nayaputta is the one name in the list that does not belong to the Buddha. Option C is wrong because it adds Nayaputta to the two real epithets. Option D is wrong because two of the three names are genuine epithets of the Buddha. Other titles of the Buddha include Sugata and Bhagavat, while Mahavira is also called Jina and Vardhamana. Exam tip: Shakyamuni and Tathagata for the Buddha, Nigantha Nataputta for Mahavira.

The correct answer is C, the lower court prohibiting continuation of proceedings in a case. Prohibition is issued by a higher court to a lower court or tribunal to stop it from acting beyond its jurisdiction. The Supreme Court issues writs under Article 32 and the High Courts under Article 226. Prohibition is preventive: it comes while the case is still pending and stops the lower court from going ahead. Its partner, certiorari, is corrective, because it quashes an order already passed without jurisdiction. Both lie only against judicial and quasi-judicial bodies, never against legislatures or private persons. Option A is wrong because commands to government officers come through mandamus, and prohibition is not issued to administrative authorities. Option B is wrong because no writ can direct a legislature to pass a law. Option D is wrong because it describes no writ; a policy is tested through judicial review. Exam tip: prohibition stops a case midway, certiorari cancels the order after it is made.

The correct answer is D, Dr. Sachchidananda Sinha. As the oldest member, he chaired the Constituent Assembly as its temporary President at its first sitting. The Assembly first met on 9 December 1946 in the Constitution Hall, now the Central Hall of Parliament, and Sinha took the chair following the French practice of letting the senior-most member preside. On 11 December 1946 Dr. Rajendra Prasad was elected the permanent President, with H.C. Mukherjee as Vice-President. Nehru moved the Objectives Resolution two days later, on 13 December 1946. Option A is wrong because C. Rajagopalachari was a member and later Governor-General, not the provisional chair. Option B is wrong because Dr. B.R. Ambedkar chaired the Drafting Committee, set up on 29 August 1947. Option C is wrong because T.T. Krishnamachari was a member of the Drafting Committee. Exam tip: 9 December 1946 first sitting under Sinha, 11 December 1946 Rajendra Prasad elected President.