单项选择题

How does water scarcity (缺乏) affect people First of all, it (51) their health. It is not that they will die (52) thirst; rather, the poor quality of the water (53) for cooking and drinking may make them ill.
(54) our bodies require water to treat waste products, plentiful water is required for propersanitation (卫生) -water (55) for much of mankind is simply not available. (56) people without adequate sanitation rose from 2.6 billion in 1990 to 2.9 billion in 1999. And sanitation is literally a matter of life and death. In a (57) statement, United Nations officials warned:" When children lack water that is fit (58) drinking and sanitation, virtually every aspect of their health and development is (59) ."
Food production is (60) on water. Many crops, of course, are watered by rain, but in recent times irrigation has become the key: (61) the world’ s booming population. Today 36 percent of the world’s harvest depends on irrigation.
If plentiful water flows out of every tap in our home and if we have a clean toilet (抽水马桶) that conveniently washes out waste, it may be (62) to believe that the world is running (63) of an adequate supply of water. We should remember, however, that only 20 percent of mankind enjoy such (64) . In Africa many women spend as much as six hours a day (65) water.