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语言朋友(100) Don't look at the sky.Don't look for old weather reports.Looking at the tree rings is more important.Correct weather reports date back only one century, but some trees can provide an exact record of weather even further back. It is natural that a tree would grow best in a climate with plenty of sunlight and rainfall.It is also expected that little sunlight or rainfall would reduce the growth of a tree.The change from a favorable to an unfavorable climate can be found out by the reading pattern of rings in a tree trunk.To find out the weather of ten years ago, you can count the rings of a tree trunk from the outside to the inside.If the tenth ring is far from the other rings, then it is certain that plenty of sunny and rainy weather occurred.If the rings are close together, then the climate was bad for the tree. Studying trees is important not only for the history of weather，but also for the history of man.In an area of New Mexico you can find only sand－no trees or people.Howevere up his mind that the people had to leave because they had cut down all the trees.Trees were necessary to make fires and buildings.So, after the people destroyed the trees, they had to move. In this example studying tree rings uncovered an exciting fact about the history of man. 解题导语：研究树的年轮不但对研究气候史有重要作用还有助于研究人类历史。________．e left | 
