During the day, you spend a lot of time running, jumping, laughing, eating, and talking. You use up a lot of energy(能量), and by the end of the day you're tired. Sleep gives your body a chance to rest.

    But your brain (大脑) and body are not completely at rest during sleep. While you sleep, your mind may think of the things that happened during the day. It keeps the important things in mind as memories(记忆). It also thinks about things you were worrying about, and you may wake up with answers to some of your problems.

    You also grow while you sleep. The thing called "human growth hormone (荷尔蒙)" in the body helps you grow during sleep. This growth hormone also helps the body to repair itself.

    Sleep helps your body to conserve energy too. You use up a lot of energy during your daily activities. But when you sleep, your body temperature falls, and your "metabolism" (新陈代谢) slows down. You are still using some energy, but much less than when you are awake and active.

    Have you ever stayed up past your bedtime? Did you have difficulty getting up the next morning? Maybe you had problems seeing clearly or you cannot think clearly. That was your body's way of saying, "I need sleep!" A lack ( 缺乏) of sleep can stop your body and mind from working correctly.

下列关于常见氧化物的叙述，不正确的是（　　）

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课外阅读。

       一百多年以前，凯巴伯森林一片葱绿，生机勃勃。小鸟在枝头歌唱，活泼而美丽的鹿在林间嬉戏。但鹿群的后面，常常跟着贪婪而凶残的狼，它们总在寻找机会对鹿下毒手。那时森林里大约有四千只鹿，人们要时刻提防狼的暗算。当地居民恨透了狼。他们组成了狩猎队，到森林中捕杀狼。

       凯巴伯森林的枪声响了25年，凯巴伯森林从此成了鹿的王国。可是，随着鹿群的大量繁殖，森林中闹起了饥荒。一切能吃得到的绿色植物，都被饥饿的鹿吃光了。整个森林像着了火一样，绿色在消退，枯黄在蔓延。紧接着，更大的灾难降临了。疾病像妖魔的影子一样在鹿群中游荡。仅仅两个冬天，鹿就死去了六万只。到1942年，凯巴伯森林只剩下了八千只病鹿。

       人们做梦也不会想到，他们捕杀的狼，居然是森林和鹿群的“功臣”。狼吃掉一些鹿，使鹿群不会发展得太快，森林也就不会被糟蹋得这么惨；同时狼吃掉的多半是病鹿，反倒解除了传染病对鹿群的威胁。而人们特意要保护的鹿，一旦在森林中过多地繁殖，倒成了破坏森林、毁灭自己的“祸首”。