1. 阅读短文，选择正确答案。

    This is the earth. The green part is land. The blue part is sea. The white part is clouds. Our earth is very beautiful and interesting. Many years ago, the earth is very clean. But nowadays there is much pollution on the earth. People are polluting the land, the water and the air. People must stop doing that. We must protect the earth.

1. （1） The          part is land on the earth.

   A . green B . white C . blue
3. （2） The white part is          .

   A . land B . sea C . clouds
5. （3） Our earth is very         .

   A . clean B . beautiful C . relaxing
7. （4） But nowadays there is much pollution on the          .

   A . tree B . earth C . land
9. （5） People are polluting          .

   A . the land and the air B . the water and the earth C . the air and the earth