What term describes rain that contains more acid than normal?

• A. Normal rain
• B. Fog rain
• C. Acid rain
• D. Pure rain

Answer: (C)

Acid rain describes rainfall that is more acidic than ordinary rain. Pollutants released from burning fossil fuels, mainly sulfur dioxide and nitrogen oxides, dissolve in water droplets in the atmosphere and react to form stronger acids like sulfuric and nitric acid. This lowers the pH of the rain compared with normal rain, which is only mildly acidic because of dissolved carbon dioxide forming carbonic acid. So the rain becomes more acidic than usual when these pollutants are present. Normal rain is just typical precipitation, and terms like fog rain or pure rain don’t capture this increase in acidity.