During the day we work and play. At night we sleep. Our body relaxes while we sleep. In the morning, we are ready to work and play again. Our body grows most while we are asleep. Children usually need m【1】 sleep. We can learn our lessons better after we have plenty of r【2】.Boys and girls need ten h【3】 of sleep every night when they are eight or nine years old. Our bodies need lots of air when we sleep. I【4】 we do not get enough fresh（新鲜的）air, we'll feel tired when we wake up. While in bed we must not cover our heads. If we do, our lungs（肺）will not get enough fresh air. If we o【5】 our windows at night we can have plenty of fresh air. Cool air is better than warm air. Boys and girls must get enough sleep if they want to s【6】 strong.