We all know that a good night's rest helps us stay healthy. After we sleep for 7 or 8 hours in bed and ____ up next morning, our mind is better prepared to memorize and learn something.

    But what about getting a rest during the middle of the day?

    Scientists say, “Short periods of sleep, napping (小睡), may help learning and memory. Napping can help young children learn better. It can ____  help older people remember longer.”

    Take China as an example. Chinese people are used to napping after lunch.

    Recently researchers made a survey among nearly 3,000 Chinese people over 65 years old. The researchers asked them ____ they napped and for how long. They found that about 60 percent of them took a nap and they napped for 60 to 90 minutes. The research shows that napping for about an hour is the best.

    However, these are the findings for those  ____ the age of 65. Doctors say that napping for about an hour may be too  ____ for young and healthy people. And they believe that half an hour is enough to ____ young and healthy people from feeling tired. By doing so, ____ will help them stay awake.

    Doctors also say, “If you have trouble falling asleep at ____ , take a daytime nap for less than 45 minutes and don't nap after 3 p.m. in the afternoon.