The world is not only hungry,but also thirsty for water. This may seem strange to you, since nearly 75 % of the earth's surface is covered with water. But about 97% of this huge amount is sea water, or salt water. Man can only drink and use the other 3% -- the fresh water that comes from rivers, lakes,underground, and other sources. And we cannot even use all of that, because some of it is in the form of icebergs and glaciers. Even worse, some of it has been polluted.
However, as things stand today, this small amount of fresh water, which is constantly being replaced by rainfall, is still enough for us. But our need for water is increasing rapidly-- almost day by day. Only if we take steps to deal with this problem now can we avoid a severe worldwide water shortage later on. A limited water supply would have a bad effect on agriculture and industry. Let me give you just one small exampie of how necessary water is to industry. Did you know that to produce a single ton of steel, it takes about 91, 000 liters of water?
We all have to learn how to stop wasting our precious water. One of the first steps we should take is to develop ways of reusing it. Experiments have already been done in this field, but only on a small scale. For us, the systems are as important as the spacecraft.
深圳市人民代表大会常务委员会公告第121号（Adopted at the Thirty-Fifth Meeting of the Standing Committee of the Third Shenzhen Municipal People‘s Congress on December 30， 2004， approved at the Sixtee...（查看全文）
Write an essay of 160—200 words based on the following drawing. In your essay, you should first describe the drawing, then interpret its meaning, and give your comment on it. You should write neat...（查看全文）
A couple order their food on the "e-menu" touch-screenRestaurants in Europe, the United States and Japan are testing technology to let diners order their food direct from a screen at their table ins...（查看全文）