摘要：The best title of this text should be . A.Soil is necessary to people B.The same crop can’t be grown in the same place every year C.Soil’s food is chemical fertilizers D.Humus is hard to make Passage 5 In the sea there are many islands. In its warm waters there are some little ones. We call them “coral Islands . A coral island is very nice to look at. It looks like a ring of land with trees, grass, and flowers on it. One part of the ring is open to the water. There is a little round lake inside the island. If you look into this lake, you will see beautiful coral. You say think they are flowers. If you look at a piece of coral, you will see many little holes in it. In each of these holes a very small sea animal has lived. These sea animals make the coral. They began to build under the water. Year after year, the coral grew higher and higher. At last it grew out of the water. Then the sea brought it small trees and something else. After some years, these things changed into earth. Sometimes the wind brought seeds to this earth. Sometimes birds flew over it and brought seeds to the island. The little seeds grew. In a few years there were plants all over the island. In a few more years there were trees growing there. So you see, these islands were built little by little. The workers were very small. Do they not teach us a lesson? Can you think what the lesson is?

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