Acid rain is a by-product of a variety of human activities that emit the oxides of sulphur and nitrogen in the atmosphere.

2SO₂ (g) + O₂ (g) + 2H₂O (l) → 2H₂SO₄ (aq)

4NO₂ (g) + O₂ (g) + 2H₂O (l) → 4HNO₃ (aq)

so the end product is (iii, iv)