Answer the following question given this paragraph: 

There are two main types of air pollutants: primary and secondary. Most air pollutants come from burning fossil fuels. Some come from burning forests. Some are due to the evaporation of chemicals.


Q: What are the two main types of air pollutants?

 Choices:

- a and b

- new and old

- good and bad

- primary and secondary

A:
primary and secondary
