21.  There is a great deal of fresh water, such as raining water, the water in rivers and lakes and so on.

22.  The amount of fresh water is so big that people can depend on it for ever.

23.  But in fact, the situation of fresh water doesn't like that people think of it.

24.  However, fresh water is in the situation of global shortage.

25.  The rapid increasing of population and the amount of using water in industry probably is the reason of causing the global shortage of fresh water.

26.  What is more, the water polution Maybe serious cause the shortage of fresh water.

27.  In the noted line , what can we do to avoid the global shortage of fresh water?

28.  If everybody realize the global shortage of fresh water and act on at once, a great deal of water will be saved.

29.  A great deal of people think that the fresh water can't be used up for , there are rains water in river, water in wells .

30.  In fact, a lot of cities is short of fresh water.