We know that trees are useful in our everyday life. They 1 us many things, such as wood, oxygen, rubber, medicine and many other things. They can 2 tell us a lot about our climate. The following are the reasons. If you 3 a tree, you can see that it has many rings (年轮). Most trees grow one new ring 4year. 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 of the tree, we can learn about the 9. We can know 10 our climate changes.