21.  By and large let all of us work hard to find ways to protect fresh water.

22.  So we must take measures to protect fresh water.

23.  Many scientists are thinking of ways to use the ice on top of the mountains, but that's not a solution, in the most important, all people on our earth should do our best to protect our fresh water .

24.  We should take measure to protect our fresh water, in case it is polluted more seriously.

25.  Last , countries should make measure to protect the oceans, rivers, to prevent them from being polluted.

26.  Therefore, we must protect the water sources and use the water limitedly .

27.  It is very important for us to protect the water source in case it might be polluted.

28.  Fresh water is shortage and important, so we can't waste water and must try our best to protect the limited sourace of fresh water.

29.  And we can plant trees to protect the environment and controll the increase of population.

30.  Every one of us should do his bit to protect the water recource , and plant more trees.