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


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

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.

 Choices:

- a and b

- new and old

- good and bad

- primary and secondary


A:
primary and secondary