51.  Fortunately, many countries in the world are taking measures to solve the important problem of fresh water shortage.

52.  Many people think that, fresh water can never be used up.

53.  The fact is that now we often face the problem of the shortage of fresh water.

54.  With the increasing of population and of industrial need of water, fresh water become shorter and shorter.

55.  Firstly, we should make best use of fresh water.

56.  Never waste fresh water.

57.  It is said that our planet is a "water" one, so people always think we have plenty of fresh water.

58.  But on the contrary, the fresh water is limited.

59.  We should also pay attention to the technology which can get fresh water from sea water.

60.  Thus, we would no longer worry about the shortage of fresh water.