Which statement best describes VOCs and their role in ozone formation?

• A. VOCs are inorganic gases that condense to form clouds.
• B. VOCs are greenhouse gases responsible for warming.
• C. VOCs are organic compounds that evaporate easily; they react with NOx in sunlight to form radicals that drive ozone formation.
• D. VOCs are particles that scatter sunlight.

Answer: (C)

VOCs are organic compounds that readily evaporate into the air. In sunlight, these vapors participate in a series of radical reactions with NOx (nitrogen oxides). The oxidation of VOCs creates peroxy and related radicals that transfer oxygen to NO, converting it to NO2. When NO2 is struck by sunlight, it splits to form oxygen atoms that combine with ambient O2 to make ozone (O3). This sequence is the main way ozone builds up in the lower atmosphere, so VOCs “drive” ozone formation by sustaining the radical chemistry that converts NO to NO2 and, ultimately, produces ozone.

That’s why this statement is the best fit: it clearly describes VOCs as organic compounds that evaporate easily and highlights their reaction with NOx under sunlight to form radicals that lead to ozone formation. The other ideas don’t match the role of VOCs in ozone chemistry—being inorganic and condensing into clouds, acting as greenhouse gases in this context, or being particles that scatter sunlight.