Answer Key
UPSC Prelims 2020, GS Paper 1: Answer Key and Subject-Wise Analysis
98 questions, cross-verified against the official UPSC answer key. Conducted 4 October 2020 (Set B, booklet code HGY-P-JHKI).
Subject distribution
Counted directly from the question bank, not estimated, so these numbers match exactly what you will see if you filter the practice list yourself.
| Subject | Questions | Share |
|---|---|---|
| Economy | 25 | 26% |
| Environment | 18 | 18% |
| Polity | 17 | 17% |
| History | 16 | 16% |
| Science & Technology | 11 | 11% |
| Geography | 6 | 6% |
| Current Affairs | 3 | 3% |
| Art & Culture | 2 | 2% |
Difficulty breakdown
Easy
9
Medium
55
Hard
34
Free
12
free to answer
Member
86
answer gated behind sign-in
Standout questions
These made aspirants pause, either because they were unusually difficult, unusually novel, or because they signal a shift in how UPSC is framing questions.
Q23 · Polity
Basic Structure Doctrine and Judicial Review
A trap built entirely on precision of language. The Constitution's text does let courts strike down laws that violate Fundamental Rights, but using judicial review specifically to protect the Constitution's basic structure is a doctrine the judiciary built itself, not something the text explicitly provides for. Both statements sound textbook-true and both are wrong.
Practise this question →Q56 · Geography
Siachen Glacier, Location
A pure map-in-the-head question. Placing the Siachen Glacier correctly, north of the Nubra Valley in the eastern Karakoram, rules out three geographically plausible-sounding but wrong options built around nearby, easily confused features.
Practise this question →Q78 · Geography
World Rivers and Their Outflow Seas
River-to-sea pairing questions reward exact recall over general awareness. The Mekong does not drain into the Andaman Sea, and the Thames does not reach the Irish Sea, two confident-sounding pairs that fail on a closer look.
Practise this question →Q64 · Environment
National Policy on Biofuels, Permitted Feedstock
The National Policy on Biofuels question turns on a single design principle rather than a list of facts, only surplus or spoiled produce like damaged grain and rotten potatoes qualifies, precisely so biofuel production never competes with the food supply.
Practise this question →Q3 · Science & Technology
Gravitational Wave Detection Missions
A pandemic-year paper still found room for frontier space science. eLISA, a proposed triangular formation of spacecraft using laser interferometry to detect gravitational waves, is easy to confuse with the very differently scaled, ground-based LIGO.
Practise this question →Key takeaways
Economy was the heaviest subject by a wide margin, 25 of 98 scored questions, with Environment close behind at 18, together well over 40 per cent of the paper. A year this Economy and Environment heavy rewards depth in agriculture, monetary policy and protected-area facts over a broad, shallow sweep.
Only 9 of 98 questions were Easy, the leanest easy-question share of any year analysed so far. A paper this technical punishes guessing and rewards precise, verified recall over general familiarity.
Art and Culture stayed the lightest subject at just 2 questions, consistent with its pattern across every year analysed, still worth its modest prep time but never the place to over-invest.
Two items (Q47, Q82) were dropped from scoring by UPSC itself, a reminder that even the official paper is not infallible, and that a dropped item is a UPSC call, not something to second-guess from outside.
What to read next
Concepts from this paper that already have a study note behind them.