题目内容：

    Studies have shown that a good night's rest helps us stay healthy, both mentally ( 精神上) and physically. Dr. Michael Twery, an expert（专家） on the science of sleep and sleep disorders, says,"Getting a 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. "

But what about getting some rest during the middle of the day? Does napping (sleeping for a short time) also 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 (遭受) 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. That only children, the very old, sick or lazy people nap is a widely-accepted opinion. However, that may be changing. Many offices now offer napping rooms, and napping cafes are appearing in many U. S. 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 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 longer periods. 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 30 minutes. But remember not to take a nap later than 3:00 in the afternoon, which may cause a sleep problem.

1.According to the passage, Dr. Michael Twery probably agrees that       

A. napping only helps the healthy, well-rested people improve their brain performance

B. napping shows people are very sick and lazy in some countries

C. people had better take a nap before 3:00 in the afternoon

D. young, healthy adults should nap longer than older people

2.The words "paying off a sleep debt" probably mean       

A. having some sleep during the work

B. making up for shortness of sleep

C. trying to sleep for longer hours

D. improving the sleep quality

3.What can we know from the passage?

A. Only the one-hour napper group finished their mental test.

B. China has the most young nappers in the whole world.

C. People should be better prepared to get a good nap.

D. More and more Americans are accepting napping.

4.Which of the following can be the best title of the passage?

A. Napping: Can It Solve Sleeping Problems?

B. Napping: How Can A Proper Nap Help?

C. Napping: Do You Really Need It?

D. Napping: flow Long Is Too Long?