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During the day we work and play, and at night we sleep. Sleep is very important. We spend about one third of our life sleeping. Our bodies rest when we sleep, so we feel fresh and energetic (精力旺盛的) the next day. Our bodies grow most when we are asleep. Children (from eight to nine) need ten hours of sleep every night. They can be better at their lessons if they have a good night's sleep.

We need plenty of air when we sleep. If not, we will feel tired when we wake up. It's a good idea to sleep with the window open, so we can have plenty of fresh air. When we are sleeping, we mustn't cover our heads or we cannot breathe (呼吸) well.