Which pollutant reacts with oxygen and hydrogen to form a major component of acid rain?

The correct answer is sulfur because it primarily contributes to the formation of acid rain through a series of chemical reactions. When sulfur dioxide (SO₂) is released into the atmosphere, often from the burning of fossil fuels, it can react with oxygen and water to form sulfuric acid (H₂SO₄). This sulfuric acid then mixes with atmospheric moisture and falls as acid rain. Acid rain can harm ecosystems, damage buildings, and affect human health.

The other pollutants listed, while significant in other environmental contexts, do not play a primary role in the formation of acid rain. Radon is a radioactive gas that poses health risks primarily through indoor air exposure rather than contributing to acid rain. Lead and mercury are heavy metals that can cause pollution and health issues, but they do not form acids that contribute to acid rain in the way sulfur compounds do.