这三段的排序该倒转过来（即321），全文该作如下：
Although the world is hungry, it is even thirsty. While nearly 3/4 of the Earth is covered with water, we are still short of drinking water. This is because about 97% of water on the earth is sea water. So we can't use it for watering plants or drinking directly. Humans can only drink and use fresh water places including rivers and lakes.
How can we avoid a serious water shortage? First, we should save water and not waste it. Second, we should protect our water resources and not pollute them. Third, we should discover ways to reuse water. Scientists have made some progress in this field. Today, some large cities are reusing their water. But people's need for water is increasing day by day. We still don't have enough water. What else can we do?
The sea seems to have the best answer. There is plenty of water in the sea. But we need to take the salt away from the sea water. This is very expensive. If scientists can find cheaper ways to do it, we can solve the problem of the shortage of water.
世界虽然饥饿，也干渴了。地球的近3/4都被水覆盖，但我们仍然面临饮用水短缺。这是因为在地球上约97％的水都是海水。因此，我们不能用它来浇花或直接饮用。人类只能食用来自淡水源的水，包括河流和湖泊。
我们怎样才能避免严重缺水？首先，我们要节约用水，不要浪费。其次，我们应该保护我们的水资源，不污染它们。第三，要研发如何将水循环再用。科学家们已在这领域取得了一些进展。如今，一些大城市正在将水循环再用。但是，人们对水的需求正与日俱增。我们还没有足够的食用水。我们还能做什么？
海洋似乎提供了最好的答案。海有大量的水。但是，我们需要将海水的盐分抽出。这是非常昂贵的。如果科学家们能找到更便宜的方法，那缺水的问题就可以解决。
~~~~~~~~~纯人手翻译，欢迎采纳~~~~~~~~~
Although the world is hungry, it is even thirsty. While nearly 3/4 of the Earth is covered with water, we are still short of drinking water. This is because about 97% of water on the earth is sea water. So we can't use it for watering plants or drinking directly. Humans can only drink and use fresh water places including rivers and lakes.
How can we avoid a serious water shortage? First, we should save water and not waste it. Second, we should protect our water resources and not pollute them. Third, we should discover ways to reuse water. Scientists have made some progress in this field. Today, some large cities are reusing their water. But people's need for water is increasing day by day. We still don't have enough water. What else can we do?
The sea seems to have the best answer. There is plenty of water in the sea. But we need to take the salt away from the sea water. This is very expensive. If scientists can find cheaper ways to do it, we can solve the problem of the shortage of water.
世界虽然饥饿，也干渴了。地球的近3/4都被水覆盖，但我们仍然面临饮用水短缺。这是因为在地球上约97％的水都是海水。因此，我们不能用它来浇花或直接饮用。人类只能食用来自淡水源的水，包括河流和湖泊。
我们怎样才能避免严重缺水？首先，我们要节约用水，不要浪费。其次，我们应该保护我们的水资源，不污染它们。第三，要研发如何将水循环再用。科学家们已在这领域取得了一些进展。如今，一些大城市正在将水循环再用。但是，人们对水的需求正与日俱增。我们还没有足够的食用水。我们还能做什么？
海洋似乎提供了最好的答案。海有大量的水。但是，我们需要将海水的盐分抽出。这是非常昂贵的。如果科学家们能找到更便宜的方法，那缺水的问题就可以解决。
~~~~~~~~~纯人手翻译，欢迎采纳~~~~~~~~~
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