Below is a chart showing the global water supply. Write an essay of about 120 words making references to the following points:
   
    1) describe the percentage of different kinds of water supply of the world;
   
    2) analyze the current situation of fresh water on earth;
   
    3) give the possible reasons for this situation.
   
    「参考范文」
   
    Water is a precious resource. Although we are surrounded by it in oceans, lakes, rivers and streams, our supply is limited. The chart given shows that most of the water on earth — 97.4 percent — is salt water stored in oceans. Only 2.6 percent of the earth's water is fresh water, and 2 percent is locked up in ice caps and glaciers. Thus the fresh water left for us to use is only 0.6 percent of the total water supply.
   
    There will never be any more fresh water than there is now. In fact, the earth is short of fresh water. Besides, the increasing growth of the world population, the growing demand of industry for water, the serious pollution of our environment — all this makes the world in danger of running out of fresh water. In some large cities such as Tianjin, fresh water cannot meet the daily needs.
   
    Since water is essential to all life and the supply limited, we must manage it intelligently and carefully.