Acid rain is caused by emissions of sulfur dioxide ($\text{SO}_2$) and nitrogen oxides ($\text{NO}_x$), which react with water molecules in the atmosphere to produce sulfuric and nitric acids. Option analysis: (A) Methane and ozone are greenhouse gases and secondary pollutants, not the primary causes of acid precipitation. (B) Sulphur dioxide and nitrous oxides are the primary acid-forming gases. (C) Methane does not cause acid rain. (D) Carbon dioxide causes normal mild rainwater acidity ($\text{pH} \approx 5.6$), but severe acid rain is due to $\text{SO}_2$ and $\text{NO}_x$.