The correct options are
B Carbon monoxide
C Sulphur dioxide
The main pollutants of air are Carbon Dioxide, Carbon Monoxide, Sulphur Dioxide, Nitrogen Oxide, and Chlorofluorocarbons, also known as CFCs.
These substances or pollutants mix up in the air in the form of gases, dust, smoke, or odor causing a smoggy situation where nothing is visible and it gets difficult to breathe.