Answer: Nitrogen oxides and hydrocarbons.
- A Carbon dioxide and water
- B Nitrogen oxides and hydrocarbons
- C Methane and surface ozone
- D Sulphur dioxide and dust
Correct answer: B. Nitrogen oxides and hydrocarbons
Explanation: Sunlight acting on NO<sub>x</sub> and unburnt hydrocarbons from vehicles produces oxidising photochemical smog (ozone, PAN, aldehydes).
Classical smog is a reducing mixture of SO₂ and fog, while photochemical smog is an oxidising mixture generated by UV-driven reactions of NOx and hydrocarbons.
Concept context
Understand how human activities alter the atmosphere, water, and soil. Covers air pollutants, smog types, ozone depletion, acid rain, greenhouse effect, water and soil pollution, and the principles of green chemistry.