Explanation
- A
Oxygen and ozone
(a) Oxygen and ozone. O2 is bulk air; ozone aloft is the shield, at ground it is a pollutant, but the pair is not the classic smog recipe in this key.
- B
Ozone and nitrogen
(b) Ozone and nitrogen. Nitrogen is inert bulk air; this pair does not name the acid-gas smog mix.
- C
Oxygen and nitrogen
(c) Oxygen and nitrogen. Ordinary dry air (~21% O2, 78% N2) is not smog.
- D
Oxides of nitrogen and sulphur
(d) Oxides of nitrogen and sulphur. Textbook smog is tied to NOx (photochemical/Los Angeles) and SOx (reducing/London, coal). (d) Official key.
Summary. Official key is (d). Smog is essentially linked to oxides of nitrogen and sulphur in the air. O2, N2 and ozone as pairs are the distractors.
Same topic · past papers
UPPSC has asked this before
These previous-year questions sit on the same topic. Open one to practise the earlier ask.
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2023 · Q52 · UPPGS
The 'Ozone layer' absorbing ultraviolet radiation exists in which atmospheric layer? -
2024 · Q108 · UPPGS
Given below are two statements, one is labelled as Assertion (A) : and the other as Reason (R). Assertion (A): CO₂, SO₂, and NO₂ gases get dissolved in rain water and produce acid rain. Reason (R): Atmospheric air is polluted due to high concentration of gases like carbon dioxide, sulphur dioxide and oxides of nitrogen. Select the correct answer from the codes given below: -
2018 · Q142 · UPPGS
Which of the following energy sources produces NO atmospheric pollution?