Question

what secondary pollutant is created by nitrogen oxides?

nitric acid

water vapor

ice crystals

pure oxygen

Explanation:

Nitrogen oxides ($NO_x$) react with water vapor and other substances in the atmosphere to form nitric acid ($HNO_3$), a secondary pollutant. Water vapor is a natural component of the atmosphere and not a pollutant formed from nitrogen oxides. Ice crystals are related to temperature and water phase changes, not nitrogen oxide reactions. Pure oxygen is a natural gas and not a pollutant created by nitrogen oxides.

Answer:

nitric acid