Final answer:
Acid rain occurs when sulfur dioxide (SO₂) and nitrogen oxides (NOx) react in the atmosphere with water to form sulfuric acid and nitric acid.
Step-by-step explanation:
Acid rain is formed due to the contribution of sulfur dioxide (SO₂) and nitrogen oxides (NOx), including nitric oxide (NO) and nitrogen dioxide (NO₂). These gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. The correct answer to the student's question is emissions of sulfur dioxide and nitrogen oxides from the combustion of fossil fuels. These reactions result in the formation of sulfuric acid and nitric acid, which lead to the acidification of rainwater, causing acid rain.