Acid rain is caused by the pollution of environment by

Answer

nitrous oxide and sulphur dioxide

(a) carbon dioxide and nitrogen: Incorrect. Acid rain is mainly caused by sulphur dioxide (SO2) and oxides of nitrogen (NOx), not atmospheric nitrogen gas; CO2 causes weak natural acidity, not acid rain in UPSC context.
(b) carbon monoxide and carbon dioxide: Incorrect. Neither CO nor CO2 is the principal cause of acid rain; the main pollutants are SO2 and NOx.
(c) ozone and carbon dioxide: Incorrect. Ozone is a pollutant in smog chemistry, but it is not the main precursor of acid rain.
(d) nitrous oxide and sulphur dioxide: Correct/closest option. Acid rain is caused by sulphur dioxide and nitrogen oxides; among the given choices, this is the intended answer because it includes SO2 and a nitrogen oxide.