UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
Who among the following rulers of Vijayanagara Empire constructed a large dam across Tungabhadra River and a canal-cum-aqueduct several kilometres long from the river to the capital city?
Answer (a) & explanation
Devaraya I built the Tungabhadra dam and canal (a). Devaraya I (1406–22) of the Sangama dynasty built a dam across the Tungabhadra and a long canal-cum-aqueduct that brought water to the capital, Vijayanagara (Hampi). This boosted farming and the state's revenue. The Portuguese visitor Nuniz described such works. Mallikarjuna (b), Vira Vijaya (c) and Virupaksha (d) were later Sangama rulers of a weaker period; none built this dam.
Notice the Italian traveller Nicolo de Conti, who visited under Devaraya I. The Hampi ruins, a UNESCO World Heritage site, still show tanks and channels, such as the stepped tank and the Kamalapura tank. The modern Tungabhadra dam came up in 1953.
Answer as per the official UPSC answer key.
Consider the following statements in respect of election to the President of India :
- 1. The members nominated to either House of the Parliament or the Legislative Assemblies of States are also eligible to be included in the Electoral College.
- 2. Higher the number of elective Assembly seats, higher is the value of vote of each MLA of that State.
- 3. The value of vote of each MLA of Madhya Pradesh is greater than that of Kerala.
- 4. The value of vote of each MLA of Puducherry is higher than that of Arunachal Pradesh because the ratio of total population to total number of elective seats in Puducherry is greater as compared to Arunachal Pradesh.
How many of the above statements are correct?
Answer (a) & explanation
Only statement 4 is correct (a). Statement 1 is wrong: only elected members of Parliament and of State Assemblies, including Delhi and Puducherry, vote; nominated members are left out. Statement 2 is wrong: an MLA's vote value is the State's 1971 population divided by its elected seats, then by 1,000, so more seats for the same population means a lower value. Statement 3 is wrong: a Kerala MLA's vote (152) is worth more than a Madhya Pradesh MLA's (131). Statement 4 is right: Puducherry's value (16) is higher than Arunachal's (8), for the reason given.
Notice that Uttar Pradesh has the highest value, 208, and Sikkim the lowest, 7. An MP's vote is the total value of all MLAs divided by the number of elected MPs, about 700.
statement 2 sounds logical but has the ratio upside down. Population is on top, seats below.
Answer as per the official UPSC answer key.
D is a 3-digit number such that the ratio of the number to the sum of its digits is least. What is the difference between the digit at the hundred's place and the digit at the unit's place of D?
Answer (c) & explanation
The difference is 8 (c). Step 1: to make (number ÷ digit sum) small, keep the hundreds digit small and the other two digits large. Step 2: with hundreds digit 1, try the best options: 199 ÷ 19 ≈ 10.47; 189 ÷ 18 = 10.5; 198 ÷ 18 = 11. So 199 is best. With hundreds digit 2, the ratio is at least 299 ÷ 20 ≈ 15. Step 3: D = 199. The difference between hundreds and units digits = 9 − 1 = 8. Options (a), (b) and (d) fail.
Tip: the hundreds digit adds 100 per unit but only 1 to the digit sum. So keep it as small as possible.
Answer as per the official UPSC answer key.
Read the passage
A global analysis of nitrogen use efficiency — a measure of the amount of nitrogen a plant takes in to grow versus what is left behind as pollution — says that using too much fertilizers will lead to increased pollution of waterways and the air. Currently, the global average for nitrogen use efficiency is approximately 0·4, meaning 40 per cent of the total nitrogen added to cropland goes into the harvested crop while 60 per cent is lost to the environment, says a study. More than half of the world’s population is nourished by food grown with fertilizers containing synthetic nitrogen, which is needed to produce high crop yields. Plants take the nitrogen they need to grow, and the excess is left in the ground, water and air. This results in significant emissions of nitrous oxide, a potent greenhouse and ozone depleting gas, and other forms of nitrogen pollution, including eutrophication of lakes and rivers and contamination of river water.
Which one of the following statements best reflects the most logical, rational and crucial message implied by the passage ?
Answer (a) & explanation
The crucial message is that better nitrogen-use efficiency is needed for both food and the environment (a). Step 1: the passage says synthetic nitrogen feeds more than half the world's people. Step 2: but only 40% of it reaches the crop; 60% is lost as pollution, including nitrous oxide. So using nitrogen more efficiently serves both food and environment. That is (a). Step 3: option (b) covers only food. Option (c), alternative crops, is not raised. Option (d) discards fertilisers that the passage calls necessary for high yields.
Tip: nitrous oxide is both a greenhouse gas and ozone-depleting. India promotes neem-coated urea and Nano urea to cut nitrogen loss.
Answer as per the official UPSC answer key.
What is the remainder if 2192 is divided by 6 ?
Answer (d) & explanation
The remainder is 4 (d). Step 1: look at remainders of powers of 2 divided by 6: 2¹ = 2 → 2; 2² = 4 → 4; 2³ = 8 → 2; 2⁴ = 16 → 4. They alternate 2, 4, 2, 4. Step 2: odd powers leave 2 and even powers leave 4. Step 3: 192 is even, so the remainder is 4. Option (c), 2, is for odd powers. Options (a) and (b) are impossible, since a power of 2 is never a multiple of 3.
Tip: for remainders of large powers, list the first few. A short repeating cycle almost always appears.
Answer as per the official UPSC answer key.
Which one of the following best describes the concept of 'Small Farmer Large Field'?
Answer (b) & explanation
Small farmers acting together as one large field (b). Under Small Farmer Large Field, neighbouring small and marginal farmers keep their own land but act as a group. They sow the same variety at the same time, buy seeds and fertiliser in bulk, hire machines jointly and sell together. This gives them the economies of scale of a big farm without giving up ownership. Option (a) describes refugee resettlement with collective farming. Option (c) describes land leasing to a company, where farmers give up control. Option (d) describes contract farming, where a company buys the crop.
Notice the link with Farmer Producer Organisations (FPOs): the government's scheme to form 10,000 FPOs follows the same idea. The model came from Vietnam's rice sector.
option (d) also involves many small farmers. In SFLF the farmers themselves organise; no company is in charge.
Answer as per the official UPSC answer key.
Consider the following statements regarding mercury pollution :
- 1. Gold mining activity is a source of mercury pollution in the world.
- 2. Coal-based thermal power plants cause mercury pollution.
- 3. There is no known ‘safe level’ of exposure to mercury.
How many of the above statements are correct?
Answer (b) & explanation
Two statements are correct (b). Statement 1 is right: small-scale gold mining, which uses mercury to bind gold particles, is the largest source of mercury released by people worldwide. Statement 2 is right: coal burning, mainly in thermal power plants, comes next, as coal holds traces of mercury. Statement 3 is wrong under UPSC's key: "no known safe level" is what the WHO says about lead. For mercury, health agencies set tolerable intake limits, though they treat it as highly toxic.
Notice the Minamata Convention (2013, in force 2017), named after Japan's mercury poisoning disaster from factory waste. India has ratified it. Mercury turns into methylmercury in water and builds up in fish, harming the brain.
the phrase "no known safe level" is borrowed from lead.
Answer as per the official UPSC answer key.
With reference to India, consider the following pairs :
| Action | The Act under which it is covered
| 1. Unauthorized wearing of police or military uniforms | The Official Secrets Act, 1923
| 2. Knowingly misleading or otherwise interfering with a police officer or military officer when engaged in their duties | The Indian Evidence Act, 1872
| 3. Celebratory gunfire which can endanger the personal safety of others | The Arms (Amendment) Act, 2019
How many of the above pairs are correctly matched?
Answer (b) & explanation
Two pairs are correctly matched (b). Pair 1 is right: the Official Secrets Act, 1923 punishes unauthorised use of uniforms (section 6), which spies could use to enter restricted places. Pair 2 is wrong: interfering with police or military officers near a prohibited place is also an offence under the Official Secrets Act (section 7), not the Indian Evidence Act, which deals only with proof in court. Pair 3 is right: the Arms (Amendment) Act, 2019 made celebratory gunfire that endangers others an offence, punishable with jail up to two years, a fine, or both.
Notice the 2019 amendment also cut the number of guns a person may hold from three to two and raised punishments for illegal arms manufacture.
Pairs 1 and 2 both belong to the Official Secrets Act. The Evidence Act defines no crimes.
Answer as per the official UPSC answer key.
Read the passage
To tackle the problem of pollution in cities, policy makers think that drastic actions like temporary use of odd-even number scheme for vehicles, closing schools, factories, construction activities, and banning the use of certain type of vehicles are a way forward. Even then the air is not clean. Vehicles more than 15 years old comprise one percent of the total; and taking them off the road will not make any difference. Banning certain fuels and car types arbitrarily is not proper. Diesel engines produce more PM 2·5 and less CO₂ than petrol or CNG engines. On the other hand, both diesel and CNG engines produce more NOₓ than petrol engines. No one has measured the amount of NOₓ that CNG engines are emitting. Arbitrary bans on vehicles that have passed mandated fitness tests and periodic pollution tests are unfair. What is needed is the scientific and reliable information about the source of pollutants on a continuing basis and the technologies that will work to reduce pollution from them.
Which one of the following statements best reflects the most logical and rational implication conveyed by the passage ?
Answer (b) & explanation
The implication is that knee-jerk reactions cannot fix pollution, but an evidence-based approach can (b). Step 1: the passage says drastic steps like odd-even and closing schools still leave the air unclean. Step 2: it ends: "What is needed is the scientific and reliable information about the source of pollutants". That is (b). Step 3: option (a) says curbs are difficult to implement; the passage calls them unfair, not hard. Option (c), heavy penalties, is not suggested. Option (d), lack of laws, is not discussed.
Tip: "unfair" and "difficult" are different complaints. Match the passage's exact objection.
Answer as per the official UPSC answer key.
Read the passage
Benefits of good quality school education accrue only when students complete and leave school after having acquired the gateway skills. Like one learns to walk before running, similarly one picks up advanced skills only after picking the basic foundational skills. The advent of the knowledge economy poses new challenges, and one of the severe consequences of having an uneducated workforce will be our inability to keep pace with the global economy. Without a strong learning foundation at the primary level, there can be no improvement in higher education or skill development.
Which one of the following statements best reflects the crux of the passage ?
Answer (a) & explanation
The crux is that to become a global power, India must invest in universal quality education (a). Step 1: the passage says advanced skills come only after foundational skills, as one walks before running. Step 2: an uneducated workforce would leave India unable to keep pace with the global economy. So universal quality schooling is the base. That is (a). Step 3: option (c) focuses on higher education, which reverses the passage's order. Option (b) says India is unable to become a power, which is too strong. Option (d), illiterate parents, is not mentioned.
Tip: India's NEP 2020 and NIPUN Bharat Mission stress foundational literacy and numeracy by Grade 3, the same idea as this passage.
Answer as per the official UPSC answer key.
Which one of the following is the best example of repeated falls in sea level, giving rise to present-day extensive marshland?
Answer (d) & explanation
The Rann of Kutch is the best example (d). The Rann of Kutch in Gujarat was once a shallow arm of the Arabian Sea. Tectonic uplift and repeated falls in sea level left behind a vast flat salt marsh that floods in the monsoon and dries into a white salt crust in winter. Option (a) is wrong: Bhitarkanika in Odisha is a deltaic mangrove forest, formed by river sediment. Option (b) is wrong: Marakkanam salt pans in Tamil Nadu are man-made. Option (c) is wrong: Naupada swamp in Andhra Pradesh is a small coastal wetland.
Notice the Rann's wildlife: it is home to the Indian wild ass sanctuary in the Little Rann and huge flocks of flamingos. Dholavira, a Harappan city, lies in the Great Rann.
Answer as per the official UPSC answer key.
With reference to Finance Bill and Money Bill in the Indian Parliament, consider the following statements :
- 1. When the Lok Sabha transmits Finance Bill to the Rajya Sabha, it can amend or reject the Bill.
- 2. When the Lok Sabha transmits Money Bill to the Rajya Sabha, it cannot amend or reject the Bill, it can only make recommendations.
- 3. In the case of disagreement between the Lok Sabha and the Rajya Sabha, there is no joint sitting for Money Bill, but a joint sitting becomes necessary for Finance Bill.
How many of the above statements are correct?
Answer (b) & explanation
Two statements are correct (b). Statement 1 is right: a Finance Bill that is not a Money Bill (an Article 117 bill) goes through the Rajya Sabha like an ordinary Bill, so the Rajya Sabha can amend or reject it. Statement 2 is right: for a Money Bill (Article 110), the Rajya Sabha can only make recommendations within 14 days, which the Lok Sabha may ignore. Statement 3 is wrong: there is indeed no joint sitting for a Money Bill, but for a Finance Bill a joint sitting is possible, not "necessary".
Notice that only the Speaker certifies a Bill as a Money Bill. The use of this route for laws like Aadhaar (2016) was challenged, and a larger bench of the Supreme Court is examining it.
"necessary" in statement 3. A joint sitting is an option the President may use, never automatic.
Answer as per the official UPSC answer key.
‘Microsatellite DNA’ is used in the case of which one of the following?
Answer (a) & explanation
Microsatellite DNA is used to study evolutionary relationships (a). Microsatellites are short DNA sequences, two to six letters long, repeated many times in a row, such as CACACA. The number of repeats varies a lot between individuals and populations. That makes them useful for DNA fingerprinting, paternity tests, wildlife forensics, population genetics and studying evolutionary relationships among species. Option (b) is about stem cells, option (c) about tissue culture and option (d) about clinical trials. "Satellite" here has nothing to do with space.
Notice India's use: the Wildlife Institute of India and CCMB's LaCONES lab use such markers to identify tiger individuals from scat and catch poachers. They also help breeding programmes avoid inbreeding.
Answer as per the official UPSC answer key.
Consider the following statements :
- Statement-I : 7th August is declared as the National Handloom Day.
- Statement-II : It was in 1905 that the Swadeshi Movement was launched on the same day.
Which one of the following is correct in respect of the above statements?
Answer (a) & explanation
Both statements are correct and II explains I (a). Statement II is right: on 7 August 1905, a meeting at the Calcutta Town Hall passed the boycott resolution against the partition of Bengal, formally starting the Swadeshi movement. Statement I is right: the government chose this date for National Handloom Day, first marked in 2015 by the Prime Minister in Chennai, because swadeshi meant using Indian-made cloth, especially handloom, and burning foreign goods. So II explains I.
Notice the swadeshi leaders: Lal, Bal, Pal, and Aurobindo. The partition took effect on 16 October 1905, which Tagore marked with Raksha Bandhan. India's handloom sector employs about 35 lakh people, many of them women, and is promoted through GI tags and India Handloom branding.
Answer as per the official UPSC answer key.
Read the passage
In India, the segregation of municipal waste at source is rare. Recycling is mostly with the informal sector. More than three-fourths of the municipal budget goes into collection and transportation, which leaves very little for processing/resource recovery and disposal. Where does waste-to-energy fit into all this ? Ideally it fits in the chain after segregation (between wet waste and the rest), collection, recycling, and before getting to the landfill. Which technology is most appropriate in converting waste to energy depends on what is in the waste (that is biodegradable versus non-biodegradable component) and its calorific value. The biodegradable component of India’s municipal solid waste is a little over 50 per cent, and biomethanation offers a major solution for processing this.
Which one of the following statements best reflects the crux of the passage ?
Answer (c) & explanation
The crux is that segregating waste is the first step to make waste-to-energy plants work (c). Step 1: the passage says waste-to-energy fits "after segregation". The right technology depends on what is in the waste. Step 2: but it opens by saying segregation at source "is rare" in India. So without segregation, these plants cannot succeed. That is (c). Step 3: option (b) calls biomethanation the most ideal way; the passage says only "a major solution". Option (a), cheap energy, is not claimed. Option (d) contradicts the "over 50 per cent" biodegradable share.
Tip: India's Solid Waste Management Rules, 2016 require segregation at source. Biomethanation turns wet waste into biogas.
Answer as per the official UPSC answer key.
Read the passage
India should ensure the growth of the digital economy while keeping personal data of citizens secure and protected. No one will innovate in a surveillance-oriented environment or in a place where an individual’s personal information is compromised. The ultimate control of data must reside with the individuals who generate it; they should be enabled to use, restrict or monetise it as they wish. Therefore, data protection laws should enable the right kind of innovation — one that is user-centric and privacy protecting.
Based on the above passage, the following assumptions have been made :
- 1. Protection of privacy is not just a right, but it has value to the economy.
- 2. There is a fundamental link between privacy and innovation.
Which of the above assumptions is/are valid ?
Answer (c) & explanation
Both assumptions are valid (c). Step 1: the passage says India should grow its digital economy while keeping personal data safe. So data protection has economic value, not just rights value (1). Step 2: it says "no one will innovate" where personal data is compromised. So privacy and innovation are closely linked (2). Step 3: so options (a), (b) and (d) fail.
Tip: India passed the Digital Personal Data Protection Act in 2023, and its rules were notified in November 2025. The Supreme Court declared privacy a fundamental right in the Puttaswamy case (2017).
Answer as per the official UPSC answer key.
Consider the following statements :
- 1. Some mushrooms have medicinal properties.
- 2. Some mushrooms have psycho-active properties.
- 3. Some mushrooms have insecticidal properties.
- 4. Some mushrooms have bioluminescent properties.
How many of the above statements are correct?
Answer (d) & explanation
All four statements are correct (d). Mushrooms are the fruiting bodies of fungi, and they are very varied. Statement 1 is right: reishi, shiitake and cordyceps are used in traditional and modern medicine. Statement 2 is right: "magic mushrooms" contain psilocybin, which acts on the mind; it is now being tested for depression. Statement 3 is right: some fungi make chemicals that kill insects, and others are used as biopesticides. Statement 4 is right: a few species glow in the dark through bioluminescence, including some found in the Western Ghats.
Notice the link with livelihoods: India promotes mushroom farming as a low-land, high-income crop, and the Gucchi mushroom of Kashmir has a GI tag.
Answer as per the official UPSC answer key.
Who among the following rulers of medieval Gujarat surrendered Diu to Portuguese?
Answer (c) & explanation
Bahadur Shah gave Diu to the Portuguese (c). Under pressure from the Mughal Humayun, Bahadur Shah of Gujarat signed the Treaty of Bassein (1534) and let the Portuguese build a fort at Diu in 1535. He was killed in 1537 during a meeting on a Portuguese ship. Option (b) is wrong: Mahmud Begarha fought the Portuguese at sea with Egyptian help, winning at Chaul (1508) but losing at Diu (1509). Option (a) is wrong: Ahmad Shah founded Ahmedabad in 1411. Option (d) is wrong: Muhammad Shah was a 15th-century ruler.
Notice that Diu stayed Portuguese until 1961, when India took Goa, Daman and Diu. Today Diu is part of the merged UT of Dadra and Nagar Haveli and Daman and Diu.
Answer as per the official UPSC answer key.
With reference to the Indian History, Alexander Rea, A. H. Longhurst, Robert Sewell, James Burgess and Walter Elliot were associated with
Answer (a) & explanation
They were associated with archaeological excavations (a). All five worked on South Indian antiquities in the colonial era. Walter Elliot dug at Amaravati in 1845. Robert Sewell listed the monuments of the Madras Presidency and wrote A Forgotten Empire (1900) on Vijayanagara. James Burgess led the Archaeological Survey of India and studied cave temples. Alexander Rea excavated the Iron Age burial site of Adichanallur in Tamil Nadu. A.H. Longhurst excavated Nagarjunakonda and wrote on Hampi. Options (b), (c) and (d) do not fit any of them.
Notice the ASI's founding by Alexander Cunningham in 1861. John Marshall later led the Harappa and Mohenjo-daro digs of the 1920s. Adichanallur is being dug again today, with Keeladi nearby.
Answer as per the official UPSC answer key.
Read the passage
The emissions humans put into the atmosphere now will affect the climate in the middle of the century and onwards. Technological change, meanwhile, could make a future transition away from fossil fuels cheap or it might not, leaving the world with a terrible choice between sharply reducing emissions at huge cost or suffering through the effects of unabated warming. Businesses that do not hedge against the threat of uncertain outcomes fail. The world cannot afford such recklessness on climate change.
Which one of the following statements best reflects the crucial message conveyed by the author of the passage ?
Answer (c) & explanation
The crucial message is that waiting for better technology before cutting emissions is unwise (c). Step 1: the passage says today's emissions will affect the climate from mid-century. Step 2: technology "could make a future transition cheap or it might not". Betting on it is reckless, like a business that fails to hedge. So act now. That is (c). Step 3: option (b) makes technology the only solution, the very gamble the author warns against. Option (a), closing businesses, and option (d), only renewable industries, are not argued.
Tip: when an author says "it might not", he is warning against relying on it. Pick the option that rejects waiting.
Answer as per the official UPSC answer key.