Which air pollutant is paired with one of its effects?

• A. Nitrogen oxides; ozone formation
• B. Particulates; visibility reduction
• C. Carbon monoxide; health effects
• D. Sulfur oxides; acid deposition

Answer: (D)

Sulfur oxides are known for producing acid deposition. When sulfur oxides from burning sulfur-containing fuels rise into the atmosphere, they react with water and other chemicals to form sulfuric acid. This acid is carried with precipitation or deposited as dry particles, lowering the pH of rain, soils, and bodies of water. The result is acid rain that can harm aquatic life, leach nutrients from soil, corrode buildings and statues, and damage ecosystems over time. This direct, well-established link—sulfur oxides leading to acid deposition—is why this pairing is the best choice.

Other options point to real effects of those pollutants—nitrogen oxides contribute to ozone formation and smog; particulates reduce visibility and affect health; carbon monoxide impairs oxygen delivery in the body—but the association between sulfur oxides and acid deposition is the clearest and most classic pairing.