Q: Acid rain may be caused by what?


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

Air pollution may also cause acid rain. This is rain that is more acidic (has a lower pH) than normal rain. Acids form in the atmosphere when nitrogen and sulfur oxides mix with water in air. Nitrogen and sulfur oxides come mainly from motor vehicle exhaust and coal burning.

 Choices:

- hurricanes

- water pollution

- volcanos

- air pollution


A:
air pollution