Rain containing acids which are harmful especially to trees and forests.

Substances such as coal and oil that were formed over millions of years from the remains of animals and plants, and are burnt for energy.

When do they collect the _______________in this neighbourhood?

I've got so much ____________________ in the garage that I need to start throwing things out.

Governments should stop factories from pumping their ____________into rivers.

People who drop _________________in the streets should be fined.