题目

The UN passed a rule in the year 2004 to improve the quality of drink water and reduce deaths caused by drinking unhealthy water each year. The UN has already worked out the specific plan to reduce half of the number, that is, five thousand. The UN announced in the world there are about 1/6 of the world population can't meet the sanitation regulation of drinking water. The water we drink and use is running short in the world. We all have to learn to stop wasting our quite limited water. One of the steps we should take is to find ways of reusing it. Experiments have already been done on this fi比较大小：    ．