Which of the following statements are true in the context of photochemical smog?

1.Photochemical smog forms from reactions between pollutants and sunlight

2.Oxides of nitrogen from burning diesel are the main pollutants causing photochemical smog

3.All hydrocarbons except methane contribute to photochemical smog

4.This smog is typically worse in summer because of more solar energy

A1, 2 and 3

B2, 3 and 4

C1, 2, 3 and 4 ✓ Correct

D3 and 4

Correct answer: (C) 1, 2, 3 and 4

Explanation

Every one of the four statements about photochemical smog is accurate, covering formation, precursors, hydrocarbons and seasonality.

Statement 1 is right: this smog forms when pollutants react under sunlight.

Statement 2 is right: nitrogen oxides from diesel burning are the chief precursors.

Statement 3 is right: every hydrocarbon except methane feeds the reactions that build the smog.

Statement 4 is right: stronger summer sunlight intensifies the photochemistry, worsening the smog.

Its irritant end products include ozone and peroxyacetyl nitrate, which sting the eyes and airways.

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