1 . Our earth is in trouble. Our drinking water is becoming dirtier, and the air is not as clear as before.   Rivers, lakes and seas    1    (pollute) by people and     2    (factory). You might think there is nothing you can do    3    (help). That’s not true. There are many things you can do.

A lot of CO₂ is produced into the air when cars burn gasoline. Some people believe that CO₂ makes the earth warmer. they think CO₂ thins the clouds above us. The clouds keep us away from     4    strongest sunlight. So try to walk, ride a bicycle     5     take a bus. And if you drive a car, drive at a steady speed. This can save some gasoline.

The biggest energy use at home is for keeping warm or cool. So turn the air conditioner(空调)     6     when you don’t   need to use it. Use lights that save energy.Use fewer things    7     cannot be used again. When you buy something, consider those    8    (make) from things that can be used again first.

Taking a shower often    9    (need) a lot of water. In one week an American family uses as much water for showers as a person drinks in three years! Buy a waterworks(供水设备) that uses    10    (little) water, or take shorter showers. This can cut the use of water.