How can photochemical smog be reduced?

• A. By reducing carbon dioxide emissions
• B. By increasing sulfur dioxide emissions
• C. By spreading more plants
• D. Through the reduction of nitrogen oxides and VOCs

Answer: (D)

Photochemical smog forms when sunlight drives reactions between nitrogen oxides from combustion sources and volatile organic compounds in polluted air, creating ground-level ozone and other oxidants. To reduce this smog, you need to limit the ingredients of that chemistry: cutting emissions of nitrogen oxides and VOCs lowers the amount of reactive partners available to form ozone. Fewer NOx and VOCs mean fewer reactions under sunlight, so less ozone production and clearer air. Other options don’t target the core chemistry: reducing carbon dioxide doesn’t directly stop the ozone-forming reactions, increasing sulfur dioxide can produce other pollution effects, and spreading more plants might help a bit but doesn’t address the primary reactants. The direct and effective approach is reducing both nitrogen oxides and VOCs.