All over the world people have cut down millions and millions of trees . Did you know man

问题补充：

All over the world ,people have cut down millions and millions of trees . Did you know many kinds of animals and plants are now disappearing ? In particular , trees are very important 1. Because they produce oxygen (氧气) and control（控制）the climate .

Now , many people are beginning to take these problems seriously . They are making wind generators (发动机) and planting new trees . There is a group in our class that picks up the garbage at school . Whether the weather is hot or cold we always do it . 2. I think we are setting a good example to everyone else.

I hope , in the future , the sky can be clearer , the water cleaner , and the land greener . Then both people and animals can have a greener Earth .因为他们制造氧气并且控制气候。

答案：

(答案→)因为他们制造氧气并且控制气候。

解析：这篇短文主要谈论了树木对于这个世界的重要性。

【小题1】注意本句中有两个并列谓语，可以翻译成两个并列分句。

【小题2】短语set a example to为……树立榜样。