I. 1. add up

   2. makes a difference

   3. paid; for

   4. throw away

   5. help out

   6. be put to good use

II. 1. mustn’t

    2. don’t have to

    3. can’t

    4. must

    5. can

III. 1. are caught

     2. has increased

     3. have shown

     4. are becoming

     5. be pulled

     6. were asked

     7. turned

IV. 1. take part in; across

     2. be harmful to / do harm to

     3. take action

     4. pulled down

     5. brings me back to

V. One possible version:

We Should Try to Protect the Environment

There are many environmental problems in recent years. Some water is polluted. Many trees are cutting down, some animals are getting less and less. Some factories are pouring dirty air into the sky. Resources are getting less and less … etc. All of these do great harm to people. They are bad for people’s health and cause diseases and death.

In order to live a better life, something must be done. We shouldn’t throw away rubbish everywhere. We should plant more and more trees in order to live better and more healthy in the future. We should try our best to protect our environment and keep the ecosystem balanced. 

To protect the environment, the governments should make more laws to control air pollution, to protect the forest and sea resources.