How is acid rain formed?

Acid rain is formed when sulfuric and nitric acids, resulting from industrial pollutants such as sulfur dioxide (SO₂) and nitrogen oxides (NOₓ), combine with rainwater. These pollutants can originate from various sources, including vehicle emissions, power plants, and industrial processes. When they are released into the atmosphere, they undergo chemical reactions, often facilitated by sunlight, transforming into acids. When it rains, these acids mix with the water droplets, resulting in precipitation that has a lower pH than normal rainwater, thus referred to as acid rain.

The other options do not accurately describe the formation of acid rain. Mixing ozone with rainwater, while ozone can contribute to air quality issues, does not lead to acid formation in the same manner as sulfuric and nitric acids. The dissolution of carbon dioxide in rainwater creates a weak carbonic acid but is not responsible for the high acidity associated with acid rain. Lastly, natural fermentation of soil does not produce the significant industrial pollutants necessary for the formation of acid rain.