We know that trees are useful in our everyday life．They give us 1 things, such as wood, oxygen, rubber(橡胶), medicines 2 many other things．They can also tell us a lot about our climate．The following are the reasons．If you cut 3 a tree, you can see that it has many rings．Most trees grow one new ring 4 year．Because of this, we know how old a tree is．A tree over a hundred 5 means that it has more than a hundred 6 ．When the climate is dry or very cold, the trees do not grow very much and their rings 7 usually thin．When it is wet and warm, the rings 8 thicker．If the rings are suddenly very thin or suddenly very thick, it means that the 9 changed suddenly．If we look at the rings on the tree, we can learn about the climate in the past years．We can see 10 changing today．
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