阅读下列短文，从每题所给的四个选项（A、B、C和D）中选出最佳选项There are many ways to help improve your health like eating healthy food. Taking exercise and getting medical help. But the easiest and cheapest way to improve your health is just to sleep eight hours or more every night. The general sleeping rule is that the younger you are，the longer sleep you need. But regardless of（不管）age，some people need to sleep more while for some a few hours is enough.
① . According to the World Health Organization over half the people in the world may be sleep﹣deprived(睡眠不足的). Having less sleep not only makes people feel tired but also causes accidents. In the United States alone, sleepy drivers cause at least 100, 000 traffic accidents a year. Also sleep problems can cause medical problems such as high blood pressure.
② . Why are so many people sleep-deprived? Part of the reasons may be cultural. In the American culture, people put a higher value on work than on sleep. In fact, people who sleep a lot are usually seen as "lazy". Also, you can sometimes hear some people say proudly that they don't have much time to sleep. They only sleep four or five hours a night. It seems that the less you sleep，the more work you'll do.
③ . How do we teach these people to learn the value of sleep? Perhaps they may listen to the advice of Dr. James Maas, an expert in sleep. He says, "Sleep is like a credit （信用卡） card. When you sleep less, you are only borrowing time. You always have to pay it back. The more hours you don't sleep, the more hours you should sleep to 'pay back' the hours on your 'sleep credit card. '"
④ . For those who value work more than sleep, they should listen to what a famous person once said. " Don't think you will be doing less work because you sleep during the night. That is a foolish idea which is held by people who have no imagination. You will be able to do more. "
