UPSC Prelims PYQs with explanations
Real questions from official papers, mapped to syllabus topics. Attempt each one; the answer and the reason appear instantly.
In which of the following regions of India are shale gas resources found?
- 1. Cambay Basin
- 2. Cauvery Basin
- 3. Krishna-Godavari Basin
Select the correct answer using the code given below.
Answer (d) & explanation
All three basins have shale gas (d). Shale gas is natural gas trapped in fine-grained shale rock, and it is extracted by horizontal drilling and hydraulic fracturing (fracking). Studies by the US EIA, ONGC and CMPDI have identified potential in the Cambay (Gujarat) (1), Cauvery (Tamil Nadu) (2) and Krishna-Godavari (Andhra Pradesh) basins (3). Other basins with potential include Assam-Arakan, the Gondwana basins (Damodar valley) and the Indo-Gangetic plains.
India's 2013 policy allowed ONGC and Oil India to explore shale in their existing blocks, and HELP (2016) now gives a single licence for all hydrocarbons. Notice the limits: fracking needs huge amounts of water and can pollute groundwater, which slows it down in water-stressed India.
Answer as per the official UPSC answer key.
Read the passage
Accountability, or the lack of it, in governance generally, and civil services, in particular, is a major factor underlying the deficiencies in governance and public administration. Designing an effective framework for accountability has been a key element of the reform agenda. A fundamental issue is whether civil services should be accountable to the political executive of the day or to society at large. In other words, how should internal and external accountability be reconciled ? Internal accountability is sought to be achieved by internal performance monitoring, official supervision by bodies like the Central Vigilance Commission and Comptroller and Auditor General, and judicial review of executive decisions. Articles 311 and 312 of the Indian Constitution provide job security and safeguards to the civil services, especially the All India Services. The framers of the Constitution had envisaged that provision of these safeguards would result in a civil service that is not totally subservient to the political executive but will have the strength to function in larger public interest. The need to balance internal and external accountability is thus built into the Constitution. The issue is where to draw the line. Over the years, the emphasis seems to have tilted in favour of greater internal accountability of the civil services to the political leaders of the day who in turn are expected to be externally accountable to the society at large through the election process. This system for seeking accountability to society has not worked out, and has led to several adverse consequences for governance.
Some special measures can be considered for improving accountability in civil services. Provisions of articles 311 and 312 should be reviewed and laws and regulations framed to ensure external accountability of civil services. The proposed Civil Services Bill seeks to address some of these requirements. The respective roles of professional civil services and the political executive should be defined so that professional managerial functions and management of civil services are depoliticized. For this purpose, effective statutory civil service boards should be created at the centre and in the states. Decentralization and devolution of authority to bring government and decision making closer to the people also helps to enhance accountability.
According to the passage, which one of the following is not a means of enhancing internal accountability of civil services ?
Answer (d) & explanation
People's participation is not a means of internal accountability (d). Step 1: the passage lists the internal means: internal performance monitoring, supervision by bodies like the CVC and CAG, judicial review of executive decisions, and the job safeguards in Articles 311 and 312. Step 2: so options (a), (b) and (c) all appear in the passage as internal means. Step 3: involving people in decisions brings government "closer to the people". That is accountability to society, which is external accountability. So (d) is the odd one out.
Tip: for a "which is NOT" question, tick off every option the passage supports. The one left over is the answer. Read the question word "not" twice.
Answer as per the official UPSC answer key.
(Same information as the question above.)
The football is in the box of which colour ?
Answer (c) & explanation
The colour of the football box cannot be determined (c). Step 1: from the earlier steps, the football is in box D. Step 2: F is indigo, so D and B share blue and yellow. Step 3: no clue tells us whether D is blue or yellow. The hockey rule fixes only F. So option (a) yellow and option (d) blue are both possible but not certain. Option (b), indigo, is wrong because F is indigo.
Tip: when two items can swap places with no rule broken, the answer is "cannot be determined". Before you choose it, check that you have used every clue. Here no clue links D or B to blue or yellow.
Answer as per the official UPSC answer key.
Read the passage
Historically, the biggest challenge to world agriculture has been to achieve a balance between demand for and supply of food. At the level of individual countries, the demand-supply balance can be a critical policy issue for a closed economy, especially if it is a populous economy and its domestic agriculture is not growing sufficiently enough to ensure food supplies, on an enduring basis; it is not so much and not always, of a constraint for an open, and growing economy, which has adequate exchange surpluses to buy food abroad. For the world as a whole, supply-demand balance is always an inescapable prerequisite for warding off hunger and starvation. However, global availability of adequate supply does not necessarily mean that food would automatically move from countries of surplus to countries of deficit if the latter lack in purchasing power. The uneven distribution of hunger, starvation, under- or malnourishment, etc., at the world-level, thus owes itself to the presence of empty-pocket hungry mouths, overwhelmingly confined to the underdeveloped economies. Inasmuch as ‘a two-square meal’ is of elemental significance to basic human existence, the issue of worldwide supply of food has been gaining significance, in recent times; both because the quantum and the composition of demand has been undergoing big changes, and because, in recent years, the capabilities of individual countries to generate uninterrupted chain of food supplies have come under strain. Food production, marketing and prices, especially price-affordability by the poor in the developing world, have become global issues that need global thinking and global solutions.
According to the above passage, which of the following are the fundamental solutions for the world food security problem ?
- 1. Setting up more agro-based industries
- 2. Improving the price affordability by the poor
- 3. Regulating the conditions of marketing
- 4. Providing food subsidy to one and all
Select the correct answer using the code given below:
Answer (b) & explanation
Statements 2 and 3 are the fundamental solutions (b). Step 1: the closing line names "marketing and prices, especially price-affordability by the poor" as the key global issues. Step 2: so improving affordability for the poor (2) and regulating marketing conditions (3) are the solutions the passage points to. Step 3: setting up agro-based industries (1) and food subsidy for all (4) are not mentioned. So options (a), (c) and (d) fail.
Tip: "according to the passage" means stick to what is written. A food subsidy for "one and all" also sounds extreme; the passage stresses the poor. In India, the National Food Security Act targets about two-thirds of the population, not everyone.
Answer as per the official UPSC answer key.
With reference to ‘Organization for the Prohibition of Chemical Weapons (OPCW)’, consider the following statements :
- 1. It is an organization of European Union in working relation with NATO and WHO.
- 2. It monitors chemical industry to prevent new weapons from emerging.
- 3. It provides assistance and protection to States (Parties) against chemical weapons threats.
Which of the statements given above is/are correct?
Answer (b) & explanation
Statements 2 and 3 are correct (b). The OPCW, based in The Hague, implements the Chemical Weapons Convention (1997). It monitors the chemical industry to stop new weapons emerging (2) and provides assistance and protection to member states against chemical threats (3). Statement 1 is wrong: it is an independent international body, not an EU organisation working with NATO and WHO.
It has 193 member states and won the Nobel Peace Prize in 2013. India signed the CWC and destroyed its declared stockpile by 2009. Notice how disarmament treaties rely on verification bodies like this.
Answer as per the official UPSC answer key.
With reference to ‘Red Sanders’, sometimes seen in the news, consider the following statements :
- 1. It is a tree species found in a part of South India.
- 2. It is one of the most important trees in the tropical rain forest areas of south India.
Which of the statements given above is/are correct?
Answer (a) & explanation
Only statement 1 is correct (a). Red sanders (Pterocarpus santalinus) is endemic to the southern Eastern Ghats, mainly the Seshachalam, Palakonda and Lankamala hills of Andhra Pradesh, with small extensions into Tamil Nadu and Karnataka. Statement 2 is wrong because it grows in dry deciduous forest on rocky, poor soil, not in tropical rainforest. So it is neither a rainforest tree nor one of the "most important" ones there.
Its deep red heartwood is prized in China and Japan for furniture and instruments, so it is smuggled heavily. It is Endangered on the IUCN Red List and listed in CITES Appendix II. The Pushpa films made this smuggling famous, and it is a favourite species question.
"Rain forest" is the error. Red sanders grows on dry, rocky hills.
Answer as per the official UPSC answer key.
Recently, linking of which of the following rivers was undertaken?
Answer (b) & explanation
The Godavari and Krishna were linked (b). In September 2015, Andhra Pradesh completed the Pattiseema lift irrigation scheme. It pumps surplus Godavari water into the Polavaram right main canal, which carries it about 174 km to the Krishna near Vijayawada (Prakasam barrage). It was the first river link actually finished in India. Cauvery–Tungabhadra (a), Mahanadi–Sone (c) and Narmada–Tapti (d) were not done then. The Par–Tapi–Narmada link has since been shelved.
Under the National Perspective Plan (1980), the Ken–Betwa link (MP–UP) is the first project under the national programme, and its foundation stone was laid in December 2024. Notice the debate around such links: they threaten forests like Panna Tiger Reserve.
Answer as per the official UPSC answer key.
There are five persons in a group — P, Q, R, S and T. The group has one doctor, one lawyer and one artist. P and S are unmarried students. T is a man married to one of the group members. Q is the brother of P and is neither doctor nor artist. R is not doctor.
Who is the doctor ?
Answer (a) & explanation
T is the doctor (a). Step 1: P and S are students, so they have no jobs. The doctor, lawyer and artist must be Q, R and T. Step 2: Q is neither the doctor nor the artist, so Q is the lawyer. Step 3: R is not the doctor, so R is the artist. That leaves T as the doctor. Options (b) P and (d) R are ruled out above, and (c) Q is the lawyer.
Tip: in grid puzzles, first remove the people who cannot hold any job. Then use the "is not" clues one at a time. Each clue usually fixes one more person. Make a small table of names and jobs and cross out boxes as you go.
Answer as per the official UPSC answer key.
Read the passage
The nature of the legal imperatives in any given state corresponds to the effective demands that state encounters, and that these, in their turn, depend, in a general way, upon the manner in which economic power is distributed in the society which the state controls.
The statement refers to :
Answer (b) & explanation
The statement shows the link between politics and economics (b). Step 1: it says laws follow the demands made on the state, and these depend "in a general way" on how economic power is spread. Step 2: so economics shapes politics, but only in a general way. That is a two-way relationship, not full control. Step 3: options (c) and (d) speak of one dominating the other, which "in a general way" does not support. Option (a), opposition between the two, is nowhere suggested.
Tip: soft words like "in a general way" or "to some extent" signal a link, not dominance. Choose the milder option when the author hedges.
Answer as per the official UPSC answer key.
A round archery target of diameter 1 m is marked with four scoring regions from the centre outwards as red, blue, yellow and white. The radius of the red band is 0.20 m. The width of all the remaining bands is equal. If archers throw arrows towards the target, what is the probability that the arrows fall in the red region of the archery target ?
Answer (c) & explanation
The probability of hitting red is 0.16 (c). Step 1: the target's diameter is 1 m, so its radius is 0.5 m. The red circle's radius is 0.2 m. Step 2: probability = red area ÷ whole area = π × 0.2² ÷ π × 0.5². The π cancels. Step 3: = (0.2 ÷ 0.5)² = 0.4² = 0.16. Option (a), 0.40, compares radii instead of areas. Option (b), 0.20, compares the red radius with the diameter. Option (d), 0.04, is just 0.2².
Tip: area grows with the square of the radius. When comparing circles, square the ratio of their radii. The widths of the other bands do not matter here.
the areas go with the square of the radius, so 0.2/0.5 = 0.4 is the trap.
Answer as per the official UPSC answer key.
In the context of the developments in Bioinformatics, the term ‘transcriptome’, sometimes seen in the news, refers to
Answer (b) & explanation
The transcriptome is the full set of RNA transcripts, mainly mRNA, that an organism or cell expresses at a given time (b). Option (a) is wrong: genome-editing enzymes such as CRISPR-Cas9 are tools, not a transcriptome. Option (c) is wrong because the transcriptome is a set of molecules, not a description of how genes are expressed. Option (d) is wrong because mutations change DNA itself.
Think of the "-omes" in a row: the genome is all the DNA, the transcriptome all the RNA, and the proteome all the proteins. Notice how comparing transcriptomes of healthy and diseased cells reveals which genes are switched on, helping cancer research and crop science.
Answer as per the official UPSC answer key.
The Montague-Chelmsford Proposals were related to
Answer (d) & explanation
The Montagu-Chelmsford proposals were constitutional reforms (d). Secretary of State Edwin Montagu's August 1917 declaration promised a step-by-step move towards responsible government. His 1918 report with Viceroy Lord Chelmsford led to the Government of India Act, 1919. It brought dyarchy in the provinces, with subjects split into transferred and reserved, a two-house central legislature, and wider separate electorates, including for Sikhs. It was not mainly about social reform (a), education (b), or police administration (c), even though education became a transferred subject.
Congress rejected the reforms as disappointing, and the Rowlatt Act came soon after. Notice the chain that followed: the Simon Commission (1927) reviewed the 1919 Act, and that led to the 1935 Act.
Answer as per the official UPSC answer key.
With reference to the Agreement at the UNFCCC Meeting in Paris in 2015, which of the following statements is/are correct?
- 1. The Agreement was signed by all the member countries of the UN and it will go into effect in 2017.
- 2. The Agreement aims to limit the greenhouse gas emissions so that the rise in average global temperature by the end of this century does not exceed 2°C or even 1.5°C above pre-industrial levels.
- 3. Developed countries acknowledged their historical responsibility in global warming and committed to donate $ 1000 billion a year from 2020 to help developing countries to cope with climate change.
Select the correct answer using the code given below.
Answer (b) & explanation
Only statement 2 is correct (b). The Paris Agreement (COP21, 2015) aims to keep the rise in global temperature well below 2°C above pre-industrial levels and to try to limit it to 1.5°C (2). Statement 1 is wrong because it came into force on 4 November 2016, after the 55-country, 55%-of-emissions threshold was crossed. Not every UN member had signed it. Statement 3 is wrong because the finance goal was $100 billion a year, not $1,000 billion, and it was a collective goal, not an admission of historical blame.
At COP29 (Baku, 2024) a new goal (NCQG) of $300 billion a year by 2035 was set. Notice that countries set their own targets (NDCs). India's include net zero by 2070 and 50% non-fossil power capacity, which it reached in 2025.
Watch the zero: the goal was 100 billion dollars, not 1000.
Answer as per the official UPSC answer key.
A class starts at 11:00 am and lasts till 2:27 pm. Four periods of equal duration are held during this interval. After every period, a rest of 5 minutes is given to the students. The exact duration of each period is :
Answer (a) & explanation
Each period lasts 48 minutes (a). Step 1: from 11:00 am to 2:27 pm is 3 hours 27 minutes = 207 minutes. Step 2: four periods have three breaks between them, because the class ends with the last period. Breaks = 3 × 5 = 15 minutes. Step 3: 4 periods = 207 − 15 = 192 minutes, so each period = 192 ÷ 4 = 48 minutes. Counting four breaks by mistake gives about 46.75 minutes, which matches no option. Options (b), (c) and (d) are all too long.
Tip: in "gaps between items" problems, n items have n − 1 gaps, like fence posts. Check: 4 × 48 + 15 = 207, which matches.
counting 4 breaks gives 46·75, which is not an option. That tells you the last break is not inside the class time.
Answer as per the official UPSC answer key.
A person walks 12 km due north, then 15 km due east, after that 19 km due west and then 15 km due south. How far is he from the starting point ?
Answer (a) & explanation
He is 5 km from the start (a). Step 1: north–south: 12 km north, then 15 km south, leaves him 3 km south of the start. Step 2: east–west: 15 km east, then 19 km west, leaves him 4 km west. Step 3: 3 km south and 4 km west form a right angle. The straight-line distance is √(3 × 3 + 4 × 4) = √25 = 5 km. Option (b), 9 km, does not fit. Option (c), 37 km, adds some of the walks. Option (d), 61 km, adds all four walks, which is total distance, not displacement.
Tip: "how far from the start" means straight-line distance. Cancel opposite directions first, then use the right-angle rule.
Answer as per the official UPSC answer key.
Which one of the following books of ancient India has the love story of the son of the founder of Sunga dynasty?
Answer (b) & explanation
Kalidasa's Malavikagnimitram tells the love story of Agnimitra, son of Pushyamitra Shunga, founder of the Shunga dynasty, for the maid Malavika at his court in Vidisha (b). Svapnavasavadatta (a), by Bhasa, is about Udayana of Vatsa. Ratnavali (d), by Harsha, also has Udayana as its hero. The Meghaduta (c) is Kalidasa's lyric poem of a yaksha sending a message through a cloud.
Pushyamitra overthrew the last Mauryan king, Brihadratha, around 185 BCE. Notice how literature can preserve history: this play is a key source on the early Shungas.
Answer as per the official UPSC answer key.
Consider the following statements :
The India-Africa Summit
- 1. held in 2015 was the third such Summit
- 2. was actually initiated by Jawaharlal Nehru in 1951
Which of the statements given above is/are correct?
Answer (a) & explanation
Only statement 1 is correct (a). The India–Africa Forum Summit held in New Delhi in October 2015 was the third one, after 2008 in New Delhi and 2011 in Addis Ababa. Statement 2 is wrong: the summit process began in 2008, not under Nehru in 1951.
The 2015 summit was the largest, with all 54 African countries taking part, and India pledged concessional credit and scholarships. Nehru's link with Africa came through anti-colonial solidarity, the Bandung Conference (1955) and the Non-Aligned Movement. Notice how India's push later helped the African Union win permanent membership of the G20 in 2023.
Answer as per the official UPSC answer key.
'Global Financial Stability Report' is prepared by the
Answer (b) & explanation
The IMF prepares the Global Financial Stability Report (b). It comes out twice a year and judges risks to the world financial system. It is one of the IMF's flagship reports, along with the World Economic Outlook and the Fiscal Monitor. The ECB (a) publishes its own Financial Stability Review for the euro area. The IBRD (c), part of the World Bank, publishes reports such as Global Economic Prospects. The OECD (d) puts out its own Economic Outlook.
In India, the RBI publishes a Financial Stability Report twice a year, drawing on the FSDC sub-committee. Notice a common trap: the Global Competitiveness Report belongs to the WEF, and the World Development Report belongs to the World Bank. Learn these by heart.
Answer as per the official UPSC answer key.
Read the passage
In general, religious traditions stress our duty to god, or to some universal ethical principle. Our duties to one another derive from these. The religious concept of rights is primarily derived from our relationship to this divinity or principle and the implication it has on our other relationships. This correspondence between rights and duties is critical to any further understanding of justice. But, for justice to be practiced; virtue, rights and duties cannot remain formal abstractions. They must be grounded in a community (common unity) bound together by a sense of common union (communion). Even as a personal virtue, this solidarity is essential to the practice and understanding of justice.
With reference to the passage, the following assumptions have been made :
- 1. Human relationships are derived from their religious traditions
- 2. Human beings can be duty bound only if they believe in god
- 3. Religious traditions are essential to practice and understand justice
Which of these assumption(s) is/are valid ?
Answer (a) & explanation
Only assumption 1 is valid (a). Step 1: the passage says "our duties to one another derive from these" religious traditions. So human relationships are drawn from religious traditions, and assumption 1 holds. Step 2: assumption 2 says duty is possible only through belief in god. But the passage allows duty to "some universal ethical principle" too. The word only makes 2 wrong. Step 3: assumption 3 says religion is essential to justice. The passage calls the balance of rights and duties, and solidarity, essential, not religion. So options (b), (c) and (d) fail.
Tip: words like only, always and essential often turn a statement false. Check whether the passage really goes that far.
Answer as per the official UPSC answer key.
Two numbers X and Y are respectively 20% and 28% less than a third number Z. By what percentage is the number Y less than the number X?
Answer (b) & explanation
Y is 10% less than X (b). Step 1: take Z = 100. Then X is 20% less, so X = 80. Y is 28% less, so Y = 72. Step 2: Y is 80 − 72 = 8 less than X. Step 3: the question asks how much less than X, so the base is X. 8 ÷ 80 = 10%. Option (d), 8%, is the trap: it divides by 100, the base of Z. Option (a), 12%, and option (c), 9%, do not fit.
Tip: in percentage comparisons, always divide by the number after "than". Taking 100 as the starting value makes these questions quick.
28 – 20 = 8% uses Z as the base.
Answer as per the official UPSC answer key.