UPSC Prelims 2019 · GS Paper I
Question 35: Environment and Ecology
Consider the following :
- 1.Carbon monoxide
- 2.Methane
- 3.Ozone
- 4.Sulphur dioxide
Which of the above are released into atmosphere due to the burning of crop/biomass residue?
AnswerUPSC’s answer is (d).
Burning crop and biomass residue releases carbon monoxide, methane and sulphur dioxide directly, along with particulates and nitrogen oxides. Ozone is not emitted directly but forms in the air when these gases and volatile organic compounds react in sunlight, and the question counts it among the pollutants due to the burning. So all four options are accepted. This is why stubble burning is linked to winter smog in north India.
- 1. Incomplete combustion releases carbon monoxide.
- 2. Biomass burning releases methane.
- 3. Ozone forms in air from the burning's gases in sunlight.
- 4. Sulphur dioxide is released from burning residue.
How you could have got this
- If you were sure statement 1 is correct, (b) goes: it leaves 1 out.
What you needed to know: Incomplete combustion releases carbon monoxide.
- Then, if you were sure statement 3 is correct, (a) and (c) go: each of them leaves 3 out.
What you needed to know: Ozone forms in air from the burning's gases in sunlight.
Only (d) is left. You didn’t need statements 2 or 4.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Sulphur dioxide and ozone are also linked to biomass burning.
- (b) Carbon monoxide is also released.
- (c) Methane and ozone are also linked to the burning.
- (d) Correct: all four are linked to burning of crop residue.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2019, General Studies Paper I, Series A. The paper on upsc.gov.in.