完型填空We know that trees are useful in our everyday life.They

完型填空
We know that trees are useful in our everyday life.They 1 us many things,such as wood,oxygen,rubber,medicines and many other things.They can 2 tell us a lot about our climate(气候).The following are the reasons(理由).If you 3 a tree,you can see that it has many rings(年轮).Most trees grow one new ring 4 year.Because of this reason,we know 5 a tree is.A tree over a hundred years old 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 are usually 7 .When it is wet and warm,the rings are much thicker.If the rings are suddenly very thin or suddenly very thick,this means that the 8 changed suddenly.If we look at the rings on this tree,we can learn about the 9 for a hundred years.We can see 10 our climate is changing today.