Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

Water is necessary for life. People can live only a few days (46) _____ it. Yet nearly 25 million people die each year because of it. Both industrial nations and less-developed countries are worried about the (47) ______ 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 (48) _____ 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 (49) ______ about water is distribution. Water is not always distributed where the large (50) ______ centers are. Some regions get enough rain, but it is all in one or two short rainy seasons.

Điền ô số 46