The world is not only hungry, but【B1】______for water. That way seems strange to you, since【B2】______75% of the earth’s surface i

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问题     The world is not only hungry, but【B1】______for water. That way seems strange to you, since【B2】______75% of the earth’s surface is covered with water. But about【B3】______of this huge amount is seawater, or salt water. Man can only drink and use the other 3%—the fresh water from rivers, lakes, underground, and other sources. And we cannot even use all of that, because some of it is in the form of【B4】______and glaciers. Even worse, some of it has been【B5】______.
    However, this small amount of fresh water is still enough for us. But our need for water is【B6】______rapidly. Only if we take steps t5 deal with this problem now can we avoid a severe【B7】______water【B8】______later on.
  【B9】______  . Today water is used only once and then discharged into a sewer system,【B10】______. But it is possible to pipe used water to a purifying plant. There it can be filtered and treated with chemicals so that it can be used again.
    But even if every large city purified and reused its water, we still would not have enough.【B11】______  If we take these steps we’ll be in no danger of drying’ up!
【B3】

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