Q: Air quality is a measure of what in the air?


Read this paragraph and choose the correct option from the provided answers:

Air quality is a measure of the pollutants in the air. More pollutants mean poorer air quality. Poor air quality started to become a serious problem after the Industrial Revolution. Factories burned coal for energy. Gasoline burned by cars and trucks added greatly to air pollution. By the mid-1900s, air quality in many big cities was very bad. Incidents in London and in U. S. cities alerted people to the extent of the problem. It was clear that air quality needed to be protected.

 Choices:

- clouds

- gases

- water

- pollutants


A:
pollutants