初中英語牛津八年級下02(2)

That's wonderful! Trees cool the air as well as clean it. Three trees can do the job of 15 air conditioners running almost all day. You certainly know a lot about trees Doctor Ray. Thank you,Judy,but I don't,really. Scientists are only now beginning to understand them. For example,did you know that when insects attack a tree, it can warn its neighbours? The trees can then protect themselves by producing a chemical that makes their leaves taste nasty. And some trees can join their roots together underground, and pass food and water around. Trees are communicating with one another, but we don't know how. Are trees in danger? In great danger. We cut down and burn millions every year but we replace hardly any of them. We are destroying our best fighters against pollution.