Of all the things we eat and drink, water is the most important. Not all people realize this, but it is quite true. The human body can live without food for a long time, but two or three days without water usually result in death. Many people do not understand how much water the human body needs, but many people do not drink enough, especially in the hot weather. Most people drink when they are thirsty but often need more water after exercises. 65 to 70 percent of the human body is water. Water is important in several different ways. Most people need five to seven liters  of water every day, but we needn't drink this amount  because a lot comes from the food we have. If we don't have enough water, however, we will feel tired and many become ill. Do you know what the best drink is? Yes, you are right. Cool water! When do we need more water?  _
In cold weather or after exercises. In hot weather or after exercises. Before breakfast, lunch and supper. When we feel tired or become ill.