Match List I with List II.

Sorting them correctly pairs a primary pollutant with carbon monoxide, a secondary one with peroxyacyl nitrate, an ozone destroyer with chlorofluorocarbons, and cloud seeds with aerosols.

Carbon monoxide is emitted directly from incomplete burning, making it a primary air pollutant.

Peroxyacyl nitrate forms in the air from reactions of other pollutants, making it a secondary pollutant.

Chlorofluorocarbons release chlorine high up that breaks down the ozone layer.

Aerosols provide tiny surfaces on which water condenses, acting as cloud condensation nuclei.

Peroxyacyl nitrate is a key ingredient of photochemical smog over cities.