阅读短文，从方框中选择适当的动词，并用其适当形式填空。有的需要加助动词或不定式符号 (每词限用一次)。

Water is very important to people. We can't live without water. There is less and less water on the earth. But some people don't seemabout that. They waste a lot of water. They pour dirty water into rivers and lakes, and theyrubbish into them. Last weekend, I decided to go to a small river to swim. But when I got there, Ithat the water in it was black.

Something mustto stop the pollution. We should save water and we should also find ways to reuse it. If we don't, wesorry in the future.