UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
Consider the following statements :
- I. It is expected that Majorana 1 chip will enable quantum computing.
- II. Majorana 1 chip has been introduced by Amazon Web Services (AWS).
- III. Deep learning is a subset of machine learning.
Which of the statements given above are correct?
Answer (c) & explanation
Statements I and III are correct (c). Statement I is right: Majorana 1 (February 2025) is a quantum chip built on "topological" qubits, expected to make quantum computing more stable. Statement III is right: deep learning, which uses many-layered neural networks, is a subset of machine learning, itself part of AI. Statement II is wrong: Majorana 1 is Microsoft's chip; Amazon's quantum chip is called Ocelot. So options (a), (b) and (d) fail.
Notice Google's quantum chip, Willow (2024). India's National Quantum Mission (2023) aims to build quantum computers with 50–1,000 qubits. A qubit can be 0 and 1 at once (superposition), which gives quantum computers their power.
Big tech firms announced quantum chips within weeks of each other in 2025: Microsoft (Majorana 1), Amazon (Ocelot) and Google (Willow).
Answer as per the official UPSC answer key.
Consider the following statements :
Statement I : Some rare earth elements are used in the manufacture of flat television screens and computer monitors.
Statement II : Some rare earth elements have phosphorescent properties.
Which one of the following is correct in respect of the above statements?
Answer (a) & explanation
Both are correct and Statement II explains Statement I (a). Statement I is right: some rare earth elements are used in flat TV screens and monitors. Statement II is right and is the reason: rare earths such as europium, terbium and yttrium are used as phosphors, the materials that glow red, green and blue in screens and LED lighting. Their light-giving property is why screens use them. So options (b), (c) and (d) fail.
Notice their other uses: neodymium magnets in EV motors and wind turbines. China controls most rare earth processing, and its export curbs in 2025 hit carmakers worldwide. India's IREL mines rare earths from beach sands in Kerala and Odisha, and a 2025 scheme backs rare-earth magnet making.
Answer as per the official UPSC answer key.
What comes at X and Y respectively in the following sequence?
January, January, December, October, X, March, October, Y, September
Answer (b) & explanation
X is July and Y is April (b). Step 1: write the months as numbers: 1, 1, 12, 10, X, 3, 10, Y, 9. Step 2: each step goes back by one more month than before: back 0 (Jan to Jan), back 1 (Jan to Dec), back 2 (Dec to Oct), back 3 (Oct to July, X = 7), back 4 (July to March) ✓. Step 3: continue: back 5 (March to October) ✓, back 6 (October to April, Y = 4), back 7 (April to September) ✓. Options (a), (c) and (d) break the pattern.
Tip: turn months or letters into numbers, and count around the circle (after 1 comes 12). Then look for steps that grow by one each time.
Answer as per the official UPSC answer key.
If N2 = 12345678987654321, then how many digits does the number N have?
Answer (b) & explanation
N has 9 digits (b). Step 1: recall the pattern: 11² = 121, 111² = 12321, 1111² = 1234321, and so on. The square rises to the number of 1s, then falls. Step 2: 12345678987654321 rises to 9, so N = 111111111, which has 9 digits. Step 3: quick check: the square has 17 digits. A number with d digits has a square of 2d − 1 or 2d digits, so d = 9. Options (a), (c) and (d) fail.
Tip: learn this palindrome pattern of repunits (numbers made of 1s). It works up to nine 1s; after that, carries spoil it.
Answer as per the official UPSC answer key.
Read the passage
Trust stands commonly defined as being vulnerable to others. Entrepreneurship implies trust in others and willingness to expose oneself to betrayal. Trust in expert systems is the essence of globalizing behaviour; trust itself emerges as a super-commodity in the social market and defines the characteristics of goods and services in a global market. Trusting conduct also means holding others in good esteem, and an optimism that they are, or will be, competent in certain respects.
Which one of the following statements best reflects the crux of the passage?
Answer (d) & explanation
The crux is that trust is important even though it carries risk (d). Step 1: the passage defines trust as "being vulnerable to others", and says entrepreneurship means a "willingness to expose oneself to betrayal". That is the risk. Step 2: it also calls trust "a super-commodity" and "the essence of globalizing behaviour". That is the importance. Both together give (d). Step 3: option (a) says trust cannot be expected in entrepreneurship, the opposite. Option (b) mixes up those who trust with those who are trustworthy. Option (c) says "no economic activity", too sweeping.
Tip: a good crux often joins two sides: "important but risky". Watch for word swaps like trusting versus trustworthy.
Answer as per the official UPSC answer key.
Consider the following statements :
Statement I : The amount of dust particles in the atmosphere is more in subtropical and temperate areas than in equatorial and polar regions.
Statement II : Subtropical and temperate areas have less dry winds.
Which one of the following is correct in respect of the above statements?
Answer (c) & explanation
Statement I is correct, Statement II is wrong (c). Statement I is right: dust in the air is highest over the subtropical and temperate belts. Statement II is wrong, because it reverses the reason: these belts have more dry winds, not fewer, and those winds lift dust from deserts and dry land, such as the Sahara, Thar and Gobi. Near the equator, heavy rain washes dust out of the air, and in polar regions, ice and snow give little dust to lift. So options (a), (b) and (d) fail.
Notice why dust matters: it acts as hygroscopic nuclei around which water condenses into clouds and rain. It also scatters sunlight, giving red sunrises and sunsets. Saharan dust even feeds the Amazon with phosphorus.
Answer as per the official UPSC answer key.
Consider the following activities :
- I. Production of crude oil
- II. Refining, storage and distribution of petroleum
- III. Marketing and sale of petroleum products
- IV. Production of natural gas
How many of the above activities are regulated by the Petroleum and Natural Gas Regulatory Board in our country?
Answer (b) & explanation
The PNGRB regulates two of these activities (b). The PNGRB Act, 2006 covers the downstream sector. Item II is right: it covers refining, storage, transport and distribution of petroleum products. Item III is right: it covers marketing and sale of petroleum products and natural gas. Items I and IV are wrong: the Act specifically excludes production of crude oil and natural gas. Upstream exploration and production come under the Petroleum Ministry and the Directorate General of Hydrocarbons.
Notice the PNGRB's other jobs: authorising city gas distribution networks and gas pipelines, and fixing pipeline tariffs. Upstream blocks are now offered under the HELP policy and Open Acreage Licensing rounds.
the Board's name has "natural gas" in it, so "production of natural gas" feels covered. Production is upstream, outside the Act.
Answer as per the official UPSC answer key.
Consider the following statements in respect of BIMSTEC :
- I. It is a regional organization consisting of seven member States till January 2025.
- II. It came into existence with the signing of the Dhaka Declaration, 1999.
- III. Bangladesh, India, Sri Lanka, Thailand and Nepal are founding member States of BIMSTEC.
- IV. In BIMSTEC, the subsector of ‘tourism’ is being led by India.
Which of the statements given above is/are correct?
Answer (d) & explanation
Only statement I is correct (d). Statement I is right: BIMSTEC has seven members. Statement II is wrong: it was founded by the Bangkok Declaration of 1997, not Dhaka 1999. Statement III is wrong: the founders were Bangladesh, India, Sri Lanka and Thailand; Myanmar joined later that year, and Nepal and Bhutan in 2004. Statement IV is wrong in UPSC's key: since its sectors were regrouped, India leads the security pillar, not tourism.
Notice the milestones: the BIMSTEC Charter came into force in 2024, and the Bangkok summit (2025) adopted the Bangkok Vision 2030. Its secretariat is in Dhaka. India sees it as a bridge between its Neighbourhood First and Act East policies.
Answer as per the official UPSC answer key.
Consider the following statements:
- I. If A ≤ B > C < D > E > F ≥ G = H; then B is always greater than E.
- II. If P > Q = R ≥ S = T ≤ U = V > W; then S is always less than V.
Which of the statements given above is/are correct?
Answer (d) & explanation
Neither statement is correct (d). Step 1: statement I: A ≤ B > C < D > E. The chain breaks at B > C < D: B and D are not linked, so B and E cannot be compared. B need not be greater than E. Step 2: statement II: S = T ≤ U = V gives S ≤ V. S could be equal to V, so "always less than V" fails. Step 3: both claims are not guaranteed. Options (a), (b) and (c) fail.
Tip: a conclusion holds only if all signs between the two letters point the same way. A "≤" in the chain means the result can be "equal", so "always less" is wrong.
a chain proves something only if every sign between the two letters points the same way.
Answer as per the official UPSC answer key.
Read the passage
It is hard to predict how changes in the climate and the atmosphere’s chemistry will affect the prevalence and virulence of agricultural diseases. But there is a risk that such changes will make some plant infections more common in all climatic zones, perhaps catastrophically so. Part of the problem is that centuries of selective breeding have refined the genomes of most high-value crops. They are spectacular at growing in today’s conditions but genetic variations that are not immediately useful to them have been bred out. This is good for yields but bad for coping with changes. A minor disease or even an unknown one could suddenly rampage through a genetically honed crop.
Which one of the following statements best reflects the central idea conveyed by the passage?
Answer (b) & explanation
The central idea is that relying fully on genetically honed crops risks food insecurity (b). Step 1: the passage says selective breeding has made crops great at growing today, but has bred out genetic variety. Step 2: so they cope badly with change: "a minor disease or even an unknown one could suddenly rampage through a genetically honed crop". That threatens food supply: (b). Step 3: option (a) talks about productivity, but the passage is about disease risk. Option (c) is vague. Option (d), replacing crops with wild varieties, is an extreme remedy the passage never suggests.
Tip: genetic uniformity is a known danger: the Irish potato famine (1840s) wiped out a crop with little variety. Seed banks protect crop diversity.
Answer as per the official UPSC answer key.
With reference to the Government of India, consider the following information :
| | Organization | Some of its functions | It works under
| I. | Directorate of Enforcement | Enforcement of the Fugitive Economic Offenders Act, 2018 | Internal Security Division-I, Ministry of Home Affairs
| II. | Directorate of Revenue Intelligence | Enforces the Provisions of the Customs Act, 1962 | Department of Revenue, Ministry of Finance
| III. | Directorate General of Systems and Data Management | Carrying out big data analytics to assist tax officers for better policy and nabbing tax evaders | Department of Revenue, Ministry of Finance
In how many of the above rows is the information correctly matched?
Answer (a) & explanation
Only one row is correctly matched (a). Row II is right: the Directorate of Revenue Intelligence (DRI) is the main anti-smuggling body, enforcing the Customs Act, 1962, under the Department of Revenue. Row I is wrong: the Enforcement Directorate does enforce the Fugitive Economic Offenders Act, 2018, along with PMLA and FEMA, but it works under the Department of Revenue, not the Home Ministry. Row III is wrong: DG Systems runs the IT systems of Customs and GST; big-data analytics to catch evaders is the job of a separate body, DGARM, under the CBIC.
Notice the trick: UPSC often gets the function right but the parent ministry wrong. Read every column. The ED was in the news for big money-laundering cases.
row III has the right parent department. The function belongs to a sister directorate with a similar name.
Answer as per the official UPSC answer key.
Regarding Peacock tarantula (Gooty tarantula), consider the following statements :
- I. It is an omnivorous crustacean.
- II. Its natural habitat in India is only limited to some forest areas.
- III. In its natural habitat, it is an arboreal species.
Which of the statements given above is/are correct?
Answer (d) & explanation
Statements II and III are correct (d). Statement II is right: the peacock tarantula (Gooty tarantula) is found only in a few forest patches of the Eastern Ghats, mainly in Andhra Pradesh. Statement III is right: it lives in tree holes, so it is arboreal. Statement I is wrong: it is a spider, an arachnid, not a crustacean, and it eats insects, not plants. So options (a), (b) and (c) fail.
Notice its status: it is Critically Endangered on the IUCN Red List, mainly due to deforestation and the pet trade, valued for its bright blue colour. It is named after Gooty town, where it was first found. Its bite is painful but rarely dangerous.
"crustacean" sounds scientific. Spiders are arachnids; crabs and prawns are crustaceans.
Answer as per the official UPSC answer key.
“Sedition has become my religion” was the famous statement given by Gandhiji at the time of
Answer (b) & explanation
Gandhi said it at the time of the Dandi Salt Law breach (b). Gandhi used the line during the Salt Satyagraha of 1930, when he openly broke the salt law and called on Indians to break British laws. Breaking an unjust law was now a duty, so in his words sedition had become his religion. The march left Sabarmati on 12 March and reached Dandi on 6 April 1930. Options (a), (c) and (d), Champaran (1917), the Second Round Table (1931) and Quit India (1942), are wrong.
Notice Quit India's own slogan: "Do or Die". Sedition was Section 124A of the IPC. The new Bharatiya Nyaya Sanhita (2023) dropped the word "sedition" but its Section 152 punishes acts endangering India's sovereignty.
Answer as per the official UPSC answer key.
Consider the following statements :
- I. The Constitution of India explicitly mentions that in certain spheres the Governor of a State acts in his/her own discretion.
- II. The President of India can, of his/her own, reserve a bill passed by a State Legislature for his/her consideration without it being forwarded by the Governor of the State concerned.
Which of the statements given above is/are correct?
Answer (a) & explanation
Only statement I is correct (a). Statement I is right: Article 163(1) itself says the Governor acts on ministers' advice "except in so far as he is by or under this Constitution required to exercise his functions… in his discretion". Examples include Article 371 duties and the Sixth Schedule. Statement II is wrong: under Article 200, only the Governor can reserve a State Bill for the President. The President cannot pull a Bill up on their own. So options (b), (c) and (d) fail.
Notice the recent fights over Governors sitting on Bills. In State of Tamil Nadu v. Governor (April 2025), the Supreme Court set time limits for assent. On a Presidential reference, a Constitution Bench in November 2025 said courts cannot fix such deadlines, but long, unexplained delay can still be reviewed.
the President is "higher", so students assume he can act directly on State Bills. The route always runs through the Governor.
Answer as per the official UPSC answer key.
Consider the sequence AB_CC_A_BCCC_BBC_C that follows a certain pattern. Which one of the following completes the sequence?
Answer (c) & explanation
The blanks are B, C, B, A, C (c). Step 1: put option (c) into the five gaps: ABBCCCABBCCCABBCCC. Step 2: it reads ABBCCC ABBCCC ABBCCC: one A, two Bs and three Cs, repeated three times. A clear pattern. Step 3: the other options do not give a repeating block. For example, (a) puts A in the last gap, breaking the CCC at the end. So (a), (b) and (d) fail.
Tip: in letter-gap series, first count the total letters (here 18) and try block sizes that divide it. Then test options quickly rather than solving from scratch.
Answer as per the official UPSC answer key.
Read the passage
There has been no democracy that has grown economically without corporate capitalism. It helps in modernizing the economy and enabling the transition from rural to urban, and agriculture to industry and services, which are inevitable with growth. It generates jobs - and there is no other way to fix a country’s unemployment challenge without a further impetus to private business. Big companies can operate on a large scale and become competitive both domestically and externally. A vibrant corporate capitalist base also leads to additional revenues for the State - which in turn, can be used for greater welfare for the marginalized and creating a more level playing field in terms of opportunities.
With reference to the above passage, the following assumptions have been made:
- I. Corporate capitalism promotes the growth of labour force and provides more employment opportunities.
- II. Poor and marginalized sections of population are benefited by corporate capitalism due to trickle-down effect.
Which of the above assumptions is/are valid?
Answer (c) & explanation
Both assumptions are valid (c). Step 1: the passage says corporate capitalism "generates jobs", and that there is no other way to fix unemployment without private business. So it expands employment (I). Step 2: it adds that a strong corporate base brings extra revenue to the State, which can fund "greater welfare for the marginalized". So the poor benefit as gains flow down (II). Step 3: both follow from the text, so options (a), (b) and (d) fail.
Tip: "trickle-down" means benefits at the top reaching the poor over time, here through taxes funding welfare. Check that each assumption has a matching line in the passage.
Answer as per the official UPSC answer key.
Fa-hien (Faxian), the Chinese pilgrim, travelled to India during the reign of
Answer (b) & explanation
Fa-hien came during the reign of Chandragupta II (b). Faxian was in India from about 399 to 412, in the reign of Chandragupta II, called Vikramaditya. He came to collect Vinaya texts on monastic rules. He wrote of a mild government, few harsh punishments, and the Chandalas living outside towns, though he never names the king. Option (a) is wrong: Samudragupta ruled before him. Options (c) and (d) are wrong: Kumaragupta I and Skandagupta came after.
Notice the other Chinese visitors: Xuanzang under Harsha (7th century) and I-tsing later, both of whom studied at Nalanda. Chandragupta II's court is linked with the "nine gems", including Kalidasa.
The Gupta pilgrim is Faxian; Xuanzang came under Harsha. Do not swap them.
Answer as per the official UPSC answer key.
With reference to monoclonal antibodies, often mentioned in news, consider the following statements :
- I. They are man-made proteins.
- II. They stimulate immunological function due to their ability to bind to specific antigens.
- III. They are used in treating viral infections like that of Nipah virus.
Which of the statements given above are correct?
Answer (d) & explanation
All three statements are correct (d). Statement I is right: monoclonal antibodies are man-made proteins, lab-made copies of one antibody. Statement II is right: each binds one specific antigen, marking the target for the immune system or blocking it. Statement III is right: they are used against viral infections; Kerala has used the monoclonal antibody m102.4 against Nipah under compassionate use. So options (a), (b) and (c) fail.
Notice their wide use: in cancer (such as trastuzumab for breast cancer), autoimmune diseases, and COVID-19. They are costly, so making biosimilars at home is a goal of India's biotech policy. The method of making them, hybridoma, won the 1984 Nobel Prize.
Answer as per the official UPSC answer key.
Consider the following statements :
- I. Indian Railways have prepared a National Rail Plan (NRP) to create a 'future ready' railway system by 2028.
- II. 'Kavach' is an Automatic Train Protection system developed in collaboration with Germany.
- III. 'Kavach' system consists of RFID tags fitted on track in station section.
Which of the statements given above are not correct?
Answer (a) & explanation
Statements I and II are not correct (a). Statement I is wrong: the National Rail Plan aims at a "future ready" railway by 2030, not 2028. Statement II is wrong: Kavach was developed indigenously by the RDSO with Indian firms, not with Germany. Statement III is right: Kavach uses RFID tags on the track, with on-board and station equipment, to apply brakes when a driver misses a signal or overspeeds. So the incorrect ones are I and II.
Notice the trap: the question asks which are not correct. Kavach is being rolled out on high-density routes like Delhi–Mumbai and Delhi–Howrah, and Kavach 4.0 was approved in 2024. Its spread gained urgency after the Balasore crash (2023).
a "not correct" question with a year changed by two. Read the numbers in the statement slowly.
Answer as per the official UPSC answer key.
Team X scored a total of N runs in 20 overs. Team Y tied the score in 10% less overs. Had team Y's average run rate (runs per over) been 50% higher, the scores would have been tied in 12 overs. How many runs were scored by team X?
Answer (d) & explanation
Team X's runs cannot be determined (d). Step 1: Y tied the score in 10% fewer overs: 18 overs. So Y's run rate = N/18. Step 2: 50% higher rate = 1.5 × N/18 = N/12. At that rate, N runs take N ÷ (N/12) = 12 overs, whatever N is. Step 3: so the second fact is automatically true and gives no new information. N can be any number. Options (a) 72, (b) 144 and (c) 216 all fit equally well.
Tip: if a "condition" turns out to be true for every value, it adds no information. Check whether each fact gives a new equation before solving.
a condition that is always true adds no information. Test it before you start solving.
Answer as per the official UPSC answer key.