Acid rain from sulfur dioxide emissions

Steps:

• Identify acid rain as precipitation with pH below 5.6, caused by atmospheric pollutants.
• Recall main pollutants: sulfur dioxide (SO2) and nitrogen oxides (NOx) from burning fossil fuels.
• Determine which option matches: sulfur dioxide is a primary contributor.
• Eliminate non-acidic gases that don't form acids in the atmosphere.

Why D is correct:

• Sulfur dioxide reacts with water vapor to form sulfuric acid (H2SO4), lowering rain pH per the reaction: SO2 + H2O → H2SO3 (sulfurous acid), which oxidizes to H2SO4.

Why the others are wrong:

• A. Methane is a greenhouse gas but does not form acids in rainwater.
• B. Nitrogen gas (N2) is inert and unreactive in the atmosphere.
• C. Oxygen is essential for life but does not contribute to acidification.

Final answer: D