1. We should try our best to __________________(保护环境)
2. Our government has done something to ________ the environment ________ (防止 ) being polluted.
3. He seldom exercises, _______ (结果), he is not in a good health.
4. The more trees we ________(砍倒), the more punishments we will get.
5. Thousands of years has passed, and many kinds of animals and plants ______________ (灭绝) as well.