Water is necessary for life. People can live only a few days (44) _____ it. Yet nearly 25 million people die each year because of it. Both industrial nations and less-developed countries are worried about the (45) ______ and quantity of water in the world.

Even though people, animals, agriculture, and industry use a lot of water, there is more than enough on the Earth. Water covers about three-fourths of the Earth's surface. However, 97.4 percent of it is salt water. Three-fourths of the Earth's fresh water is frozen in glaciers and in the great polar ice caps. Most of the water we use (46) _____ from rivers, lakes, and the atmosphere. Less than one percent of the Earth's water is usable, and we use it over and over again.

One of the (47) ______ about water is distribution. Water is not always distributed where the large (48) ______ centers are. Some regions get enough rain, but it is all in one or two short rainyCâu 47.