听录音，写单词，补全短文。

The Earth is a place. There are , rivers, mountains and . Some parts of the Earth are hot, but some parts are very cold. There are many kinds of and plants on the Earth. Some are , but some are small. Today some parts of the Earth are very . People throw into the rivers. Some people cut down too many trees. They pollute the , the water and the . It is important for us to the Earth.