Nitrogen fertilizer impacts: eutrophication yes, smog no

Steps:

• Excess ammonium nitrate adds nitrogen to soil, which runs off into rivers.
• Runoff causes eutrophication, boosting algae and plant growth in water bodies.
• Ammonium nitrate decomposes to ammonia or nitrates, not atmospheric NOx/VOCs needed for smog.
• Thus, river growth occurs, but photochemical smog does not.

Why B is correct:

• Eutrophication from nitrate runoff directly increases aquatic plant growth, per nutrient pollution definitions.

Why the others are wrong:

• A: Wrongly links fertilizer to photochemical smog, which requires vehicle emissions, not soil nitrates.
• C: Falsely denies river plant growth, ignoring eutrophication from nitrogen excess.
• D: Incorrectly denies both effects, overlooking runoff's role in water pollution.

Final answer: B