Acid rain from sulfur and nitrogen oxides

Steps:

• Recall acid rain forms when pollutants react with atmospheric water to create acidic precipitation.
• Identify key pollutants: sulfur dioxide (SO₂) from burning fossil fuels and oxides of nitrogen (NOx) from vehicle emissions and combustion.
• Note these gases dissolve in water vapor, forming sulfuric acid (H₂SO₄) and nitric acid (HNO₃).
• Match to options: only D lists both SO₂ and NOx.

Why D is correct:

• SO₂ and NOx react with water via H₂SO₄ from SO₂ + H₂O and HNO₃ from NOx + H₂O, lowering rain pH below 5.6 per environmental science definitions.

Why the others are wrong:

• A: CO₂ and CH₄ are greenhouse gases, not acid-formers.
• B: Oxygen is abundant but inert; NOx alone insufficient without SO₂.
• C: CH₄ is a greenhouse gas; SO₂ alone doesn't fully cause acid rain.

Final answer: D