Why should carbon dioxide be classified as an air pollutant? 

A)  because the concentration in the atmosphere is decreasing 
B)  because it is depleting the ozone layer and increasing skin cancer rates 
C)  because it is contributing to global warming 
D)  because the stratosphere is warming and carbon dioxide plays a role

Air Pollutant

Substances in the air that can have harmful effects on the health of living creatures or the environment, including gases, particulates, and biological molecules.

Global Warming

The ongoing rise in Earth’s surface temperature, primarily due to the emission of greenhouse gases from human activities, leading to climate change and associated impacts.

Stratosphere

The layer of the Earth's atmosphere located above the troposphere, characterized by a slight temperature increase with altitude and the presence of the ozone layer.