Answer:
2. D
3. A
4. C
Step-by-step explanation:
Sulphur dioxide dissolves in rainwater, giving rise to acid rain in option D, but sulphur dioxide wasn't included in D's option but acid rain.
Smog is a combination of smoke, chemical pollutants and water droplets. it reduces visibility.
Carbon monoxide is formed when fuel is burnt incompletely. Like in vehicle exhaust.