Answer: spring.
- A spring
- B summer
- C autumn
- D winter night
Correct answer: A. spring
Explanation: Polar stratospheric clouds in the cold winter set up conditions so that ozone is destroyed rapidly in the returning spring sunlight.
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.