Which of the following is a secondary pollutant ? A. NO B. CO C. SO2 D. PAN

The correct answer is D. PAN.

Primary pollutants are pollutants that are emitted directly into the air from a source, such as a power plant or car exhaust. Secondary pollutants are pollutants that are formed when primary pollutants react with other chemicals in the air.

NO, CO, and SO2 are all primary

pollutants. PAN is a secondary pollutant. It is formed when NO2 reacts with hydrocarbons in the presence of sunlight.

PAN is a very reactive pollutant that can damage plants and animals. It can also cause respiratory problems in humans.