The earth is our home．We must take good care of it．This means to keep the land，air and water clean．But pollution is a serious problem．To pollute
means to make things dirty．Pollution appears in many forms．We can see it，smell it and drink it．pollution is beginning to do harm to our life．
Man has been polluting the earth from the time he first made his fire，washing his clothes in the river and throwing his rubbish on the ground．Long，long ago，the problem was not so serious because there were not so many people．There are more and more people in the world．From last century，man had polluted the world more and more and the environment was getting worse and worse．
Talking about pollution，we once only meant air pollution．It is true that air pollution is still the most dangerous Now，but it is only one kind of pollution.For example，by using poison，we have polluted the land and killed the animals．By putting dirty water into rivers and lakes，we have polluted Our drinking water and killed the fish and so on．
The more people there are，the more rubbish there will be．If we want to stop pollution，we should keep the population from growing too fast．
(1)
What can we do to take care of the earth?
(2)
Is pollution harmful to our life?
(3)
When has man been polluting the earth?
(4)
Do you think if there are too many people in the world?