31.  First is to save up the fresh water, anyone can and must do it.

32.  Second, Scentist should research how to covert sea water into fresh water, that means we students should study hard to do it .

33.  Fresh water is indispensable to the dialy live of mankind.

34.  People ever thought fresh water is countless, it May come from many sources, such as rain, river, well.

35.  In fact, fresh water is very short, especially now.

36.  During these years, population increased fastly , more and more fresh water are needed.

37.  Worst of all, plenty of fresh water is being polluted.

38.  Man is in short of fresh water.

39.  Since fresh water is limited and short , it's high time that we did what we can to avoid the crisis.

40.  Meanwhile, we should establish laws to stop pollution, otherwise the shortage of fresh water will prevent us from developing quickly.