Detailed Explanation:

Answer: Option 2 — 2 and 4 only

Acid rain is caused by the presence of nitrogen oxides (NOₘ) and sulphur dioxide (SO₂) in the atmosphere, which react with water vapor to form nitric acid and sulphuric acid respectively. Carbon monoxide and ozone are pollutants but do not directly contribute to acid rain formation.

✅ Statement 2 – Correct: Nitrogen oxides (NOₓ) react with water and oxygen in the atmosphere to form nitric acid (HNO₃), a primary component of acid rain.
❌ Statement 1 – Incorrect: Carbon monoxide (CO) is a pollutant that contributes to ground-level ozone formation but does not cause acid rain.
❌ Statement 3 – Incorrect: Ozone (O₃) is a secondary pollutant and does not act as a precursor for acid rain formation.
✅ Statement 4 – Correct: Sulphur dioxide (SO₂) reacts with atmospheric moisture to form sulphuric acid (H₂SO₄), the other major component of acid rain.

📝 Short Notes: Acid Rain

• Definition: Acid rain refers to precipitation (rain, snow, fog) with a pH below 5.6, caused by atmospheric pollution.
• Primary Causes: Emissions of sulphur dioxide (SO₂) from coal combustion and nitrogen oxides (NOₓ) from vehicle exhausts and industrial processes.
• Chemical Reactions: SO₂ + H₂O → H₂SO₃ (sulphurous acid) → H₂SO₄ (sulphuric acid); NOₓ + H₂O → HNO₃ (nitric acid).
• Environmental Effects: Acidification of lakes and streams, damage to forests, corrosion of buildings and monuments (especially marble and limestone), soil degradation.
• Human Health Impact: Respiratory problems due to fine particulate matter formed from SO₂ and NOₓ.
• Control Measures: Use of low-sulphur fuels, installation of scrubbers in industries, catalytic converters in vehicles, and promotion of renewable energy sources.