Natural pollutants can play an important role in controlling air pollution for which of the following reasons?

* Hướng dẫn giải

Dẫn chứng: Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides, are found in nature. As the Earth developed, the concentrations of these pollutants were altered by various chemical reactions; they became components in biogeochemical cycles.