Matching Pollutant Sources to Natural Processes

Steps:

• Recall methane (CH₄) forms from anaerobic decay of organic matter like plants in wetlands.
• Recall sulfur dioxide (SO₂) releases from volcanic gases during eruptions.
• Examine choices: First item pairs with methane, second with SO₂.
• Select option with accurate pairs: decaying plants for methane, volcanoes for SO₂.

Why A is correct:

• Decaying plants generate methane via microbial methanogenesis in oxygen-poor environments; volcanoes emit SO₂ directly from sulfur-rich magma per volcanic gas composition data.

Why the others are wrong:

• B: Lightning produces nitrogen oxides (NOₓ), not methane; photochemical reactions create ground-level ozone from VOCs and NOₓ, not SO₂.
• C: Lightning does not produce methane; volcanoes are correct for SO₂ but the methane pair fails.
• D: Identical to B, so both sources are mismatched.

Final answer: A