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Topic Atmospheric composition
Asked 7 times across 4 UPSC exams over 7 years (2018–2025), peaking in 2025.
Key insights
- Most tested in GEO — 3 of 7 PYQs
- First appeared in CDS 2018 — 6 years before CSE 2024 (allied exams preview CSE)
- Most asked in 2025
- Recurs across 5 years (2018–2025)
How it travelled across exams
First appearance in each exam — the same idea, reframed.
CDS 2018 → GEO 2021 → CISF 2022 → CSE 2024
How the concept evolved
Rising — more than half its appearances (7 of 7) are since 2016.
Sample questions
You've seen the pattern — here are a few of the actual PYQs.
CISF2025
Which of the following are the major constituents of dry air in the lower atmosphere ?
- A Water vapour and oxygen
- B Nitrogen and oxygen ✓
- C Nitrogen, oxygen and methane
- D Nitrogen, oxygen, water vapour and methane
✓ Correct answer: (B)
Geography › Climatology
GEO2025
Among the following, which one is the least in percentage by volume in the atmosphere?
- A Hydrogen ✓
- B Argon
- C Helium
- D Neon
✓ Correct answer: (A)
Geography › Climatology
CSE2024
With reference to "water vapour", which of the following statements is/are correct ?
- It is a gas, the amount of which decreases with altitude
- Its percentage is maximum at the poles. Select the answer
using the code given below :
- A 1 only ✓
- B 2 only
- C Both 1 and 2
- D Neither 1 nor 2
✓ Correct answer: (A)
Geography › Climatology
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