阅读下列材料,从每题所给的A、B、C、D四个选项中,选出最佳选项。
Studies have shown that a good night's rest helps us remain healthy, both mentally and physically. Dr. Michael Twery, an expert on the science of sleep and sleep disorders, says, "Getting good night's sleep is important for learning because it stores the training and learning exercises into our long-term memory while we're sleeping 7 to 8 hours. And then the next morning, our mind is better prepared to perform."
Then what about getting some rest during the middle of the day? Does anapalso help our brain work better? If it is really helpful, then how long can a proper nap last?
Napping can help babies and young children learn better. Also, it can stop older people suffering from memory loss. Some people have sleep problems at night, so they nap during the day as a way of paying off a sleep debt. They hope napping may make them feel less tired and sleepy during the day.
In America, it is a shame for people to admit (承认)that they do take a nap. They suppose napping shows they are weak or short of energy. It is a widely-accepted opinion that only children, the very old, sick or lazy people nap. However, that may be changing. Many offices now offer napping rooms, and napping cafes are appearing in many US cities.
Unlike America, napping is part of a normal, everyday life in other parts of the world. For example, China is generally considered as a land of nappers. Researchers found nearly 60 percent of old Chinese people took a nap after lunch and most of them napped for about an hour. The study also found that people who took an hour-long nap did much better on mental tests than those who did not nap or who napped for a longer period. It seems that the most helpful nap lasted for about an hour.
But Dr. Michael Twery mentions that an hour-long nap may be too long for young, healthy adults. "We're suggesting that we try to nap for about 30 minutes or less. And 30 minutes is enough to help us feel more awake." He also found that someone who naps because of bad sleep at previous night may not experience the same improvements from napping as a healthy, well-rested person would. So, the right thing to do is to get enough sleep at night and take a proper nap for about 30minutes. But remember not to take a nap later than three o'clock in the afternoon, which may cause a sleep problem.