Explanation
- A
1 and 2 only
(a) 1 and 2 only. Crop-residue burning emits carbon monoxide and methane, but ozone (as a secondary pollutant from precursors) and sulphur dioxide are also in the mix, so 1-and-2 is not the key.
- B
2, 3 and 4 only
(b) 2, 3 and 4 only. Drops carbon monoxide, a primary incomplete-combustion gas from stubble fires, so this is not the key.
- C
1 and 4 only
(c) 1 and 4 only. Incomplete relative to the full emission set, so not the key.
- D
1, 2, 3 and 4
(d) 1, 2, 3 and 4. Open burning of crop/biomass residue releases CO, methane, SO2 and precursors that form ozone, along with PM2.5. All four listed gases are therefore associated with that burning, and this is the official key.
Summary. Official key is (d) all four. Stubble and biomass fires are incomplete combustion: carbon monoxide, methane, sulphur dioxide and ozone-related photochemistry plus particulates. North Indian winter smog questions often sit next to this fact. Honour the stored letter (d).
Same topic · past papers
UPSC has asked this before
These previous-year questions sit on the same topic. Open one to practise the earlier ask.
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2022 · Q100 · General Studies · 2 marks
Consider the following: 1. Carbon monoxide 2. Nitrogen oxide 3. Ozone 4. Sulphur dioxide Excess of which of the above in the environment is/are cause(s) of acid rain? -
2021 · Q17 · General Studies · 2 marks
Why is there a concern about copper smelting plants? 1. They may release lethal quantities of carbon monoxide into environment. 2. The copper slag can cause the leaching of some heavy metals into environment. 3. They may release sulphur dioxide as a pollutant. Select the correct answer using the code given below -
2024 · Q90 · General Studies · 2 marks
According to the Environmental Protection Agency (EPA), which one of the following is the largest source of sulphur dioxide emissions ? -
2020 · Q79 · General Studies · 2 marks
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2019 · Q43 · General Studies · 2 marks
In the context of proposals to the use of hydrogen- enriched CNG (H-CNG) as fuel for buses in public transport, consider the following statements: 1. The main advantage of the use of H-CNG is the elimination of carbon monoxide emissions