Go back to the text and find the words and phrases in bold to replace the underlined phrases in the sentences below.

1 A lot of ecological catastrophes occur because people do not observe safety regulations.

2 Factories and plants release a lot of waste into the air and water.

3 In summer a lot of young people join groups of volunteers to take care of animals in wildlife reserves.

4 It is not cost-effective to work hard on the effects of the pollution problem. It’s much better to deal with its cause.