Acid rain is caused by the pollution of environment by

Answer: (d) Nitrous oxide and Sulphur dioxide

Nitrogen oxides and sulphur dioxide form nitric and sulphuric acid.

The idea

Clean rain is already slightly acidic, about pH 5.6, because carbon dioxide in the air dissolves in it to form weak carbonic acid. That is natural and harmless. Rain becomes “acid rain” only when stronger acids from sulphur and nitrogen oxides are added.

CO₂ + water → weak carbonic acid → pH 5.6 (normal) → SO₂ and NOₓ + water → strong acids → pH below 5.6 (acid rain)

Why the others are wrong

(a) CO₂ makes rain slightly acidic (pH 5.6) — that is normal; nitrogen gas is inert.

(b) CO doesn’t form acids.

(c) Ozone is not an acid-former.

The trap

The question uses “nitrous oxide” (N₂O) loosely for nitrogen oxides. The real acid-rain gases are SO₂ and NO/NO₂, not N₂O.

Also know

Acid can come down wet (rain, snow, fog) or dry (gases and particles settling on surfaces). Tall chimneys do not solve the problem: they carry the gases far away, and the acid falls hundreds of kilometres from the source.