用方框中所给单词的适当形式填空，每词仅用一次（每空一词）。

The most important drink is water. Not many people understand this but it is ____ . People can’t _____ if they don’t drink water two or three days. In hot whether, many people don’t drink _____water, because they don’t know how much water they need. After _____ exercise, people need more water. Water is _____ to all the living things. “ There will be no life if there is no water.