We know that trees are useful in our everyday life. They1 us many things, such as wood, oxygen, rubber, medicines and many other things. They can2 tell us a lot about our climate(气候）. The following are reasons. If you3 a tree, you can see that it has many rings(年轮). Most trees grow one new ring4 year. Because of the reason, we know5 a tree is. A tree over a hundred years old means that it has more than a hundred6 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 8changed suddenly. If we look at the rings on this tree, we can learn about the 9 for a hundred years. We can see10 our climate is changing today.

—My daughter hasn't come back from school yet. I        for her.

    Trees are useful to man in three important ways.

    The first important way is that they provide man with wood and other products. Trees provide not only man but also many animals with food. Without trees, many animals could not live on the Earth. It's not easy for man to live on the Earth either.

    The second important way is that trees give us shade. On a hot summer day, people are eager（渴望）to have a rest under the tree after they have a long walk. You can imagine how important the shade of a tree is to man and animals.

    The third important way is that trees help to prevent droughts and floods. However, in many parts of the world, people haven't realized the third way. They cut trees down in large numbers. In the end, they find that they have lost the best friends they had.

—I(do) my homework.