短文改错。 假如英语课上老师要求同学们交换修改作文,请你修改你同桌写的以下作文.

题目：

短文改错。

假如英语课上老师要求同学们交换修改作文,请你修改你同桌写的以下作文.文中有10处错误,要求你在错误的地方增加、删除或修改某个单词.

增加:在缺词处加一个漏字符号(∧),并在其下面写上该加的词.

删除:把多余的词用斜线(＼)划掉.

修改:在错的词下划一横线,并在该词下面写上修改后的词.

注意:1. 每处错误及其修改均仅限一词.

2. 只允许修改10处,多者(从11处起)不计分.

The world is not only hungry, but also thirst. This may sounds strange, since nearly seventy percent of

the earth's surface is covered with water. But about ninety percent of this is sea water. Man and most

of the animals can only drink and use the remained ten percent of water --- fresh water. The need for

water is increased day by day. Only when steps are taken to deal with this problem immediate can we

avoid a severe worldwide water shortage later on. One of the first steps are to develop ways to reuse

them. Experiments have already carried out in this field. The used water has been pumped to a water

purifying plant that it can be separated from waste matters and treated with chemicals so that it can be

reused again.