完形填空阅读下面短文, 掌握其大意, 然后从各题所给的四个选项(A、B、C和D)中, 选出最佳选项. Of all the things we eat and drink, water is __1__ important. Not many people realize(意识到) this, __2__ it is quite true. The human body can go __3__ food for a long time, but two or three days without water usually leads to(导致) __4__. __5__ people do not understand how much water the human body needs __6__ work and many people do not __7__ enough especially(特别是) in hot weather. Most people drink enough __8__ in hot weather. Most people drink when they are __9__, but we often need more __10__, especially when we have been doing exercise. A man's body is 65 ～ 75 % water. Water is very important in several different __11__. Most people need __12__ five to seven liters(升) of water every day, but we do not need __13__ that mount, because a lot of water __14__ from the food we eat. If we do not have enough water, however, we feel __15__ and may become ill. Do you know what the best drink is