题目内容：

Can trees talk? Yes, not in words. Scientists have reasons to believe that trees do communicate 1. each other.

Not long ago, researchers 2.(learn) some surprising things. First a willow tree 3.(attack) in the woods by caterpillars(毛虫) changed the chemistry of its leaves and made them taste so terrible that they got tired of the leaves 4.(gradual) and stopped eating them. Then even more 5.(astonish), the tree sent out a special smell—a signal causing 6. neighbors to change the chemistry of their own leaves and make them less tasty.

Communication, of course, doesn’t need to be in words. We can talk to each other by smiling, raiding our shoulders and moving our hands. 7. we know is that birds and animals use a whole vocabulary of songs, sounds, and movements. Bees dance their signals. 8.(fly) in certain patterns that tell other bees where 9. (find) nectar(花蜜) for honey. So why shouldn’t trees have 10.(way) of sending messages?