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“Do you get enough sleep?” The answer is probably no if you ask a tired student who is always taking a nap（小睡）on a classroom desk. “I couldn’t get to sleep and experienced a restless night again.” You may often hear such words from an adult. Not having enough （1） is a common problem around the world.

However, sleep is just like food and water to us. （2） of us can live if we don’t sleep at all. Sleep experts say that an adult requires 7 to 9 hours of sleep a night and a teenager needs 8.5 to 9.5 hours. Anything less could be h （3） to our health.

According to a study, sleeping only five hours a night for a week is like having a blood-alcohol（酒精）level of 0.1 percent. That is above the safe driving limit（限制）in most countries. Most people probably wouldn’t take an exam or go to work if they get drunk. But （4） enough sleep, they still do these things. As a result, they （5） in the exams or perform badly at work. What’s worse, doctors and nurses often work long hours. When they are sleepy, they might hurt a patient or even （6） a patient’s death by accident.

（7） sleep is so important, many people these days are not getting enough. In a survey, twenty percent say that daytime sleepiness influences their daily work. They feel it hard to pay full attention during the day. However, they don’t seem to care. Some even show off how energetic they can be the next day just with little sleep. It may be time to wake up and （8） the way we think. We should realize that not sleeping enough is a serious problem.