Q.Which of the following is a secondary pollutant?

Tropospheric pollution is the build-up of undesirable solid or gaseous particles in the near-ground air where humans live. It has two broad classes: gaseous air pollutants — oxides of sulphur, nitrogen and carbon, hydrocarbons, ozone and other oxidants — and particulate pollutants such as dust, mist, fumes, smoke and smog. Gaseous pollutants are produced mainly by burning fossil fuels in vehicles, power plants and industry, while particulates arise from combustion, mechanical processes like crushing and grinding, and condensation of vapours. Tropospheric pollution drives most of the everyday air-quality problems people experience — respirat …