Acid Rain Formation and Causes

Acid rain is primarily caused by sulfur dioxide (SO₂) and nitrogen oxides (particularly nitrous oxide/NO and nitrogen dioxide/NO₂) released from burning fossil fuels and industrial activities. These gases react with water vapor in the atmosphere to form sulfuric acid (H₂SO₄) and nitric acid (HNO₃), which fall as acid rain. Option (a) is incorrect because while nitrogen is involved, carbon dioxide does not cause acidity. Option (b) is wrong because carbon monoxide and carbon dioxide do not form acid rain. Option (c) is incorrect; ozone does not cause acid rain. The primary culprits are sulfur dioxide and nitrogen oxides, which directly form acids when combined with atmospheric moisture. This is a well-established environmental science concept. > Acid rain chemistry: SO₂ + H₂O → H₂SO₄; NOₓ + H₂O → HNO₃ — sulfur dioxide and nitrogen oxides are the key pollutants. Answer: (d).