One day, a lobster(龙虾) met a hermit crab(寄居蟹)in the deep sea. They stopped {#blank#}1{#/blank#} (swim) and began to have a talk with each other.

    The lobster {#blank#}2{#/blank#} (take) off his hard shell and showed his lovely and soft body. When the hermit crab saw the lobster take off the shell, {#blank#}3{#/blank#}felt surprised. He shouted at the lobster and wanted to stop the lobster.

    "Hey!" said the crab. “{#blank#}4{#/blank#} are you talking off your shell? The shell is {#blank#}5{#/blank#} (use) and it can protect you. Now you take off your shell. Big fish may eat you. You may also knock against a rock. Don't be silly. Please put {#blank#}6{#/blank#} your shell again. Or you will have to {#blank#}7{#/blank#} (payment) a heavy price for what you did."

    “{#blank#}8{#/blank#} (thank) for your reminding, hermit crab! But we take off our shells in order {#blank#}9{#/blank#} (grow) better. {#blank#}10{#/blank#}we are afraid to take off our shells, then we can't move forward in life," answered the lobster.

    The hermit crab thought it over and understood what the lobster said.

    We all know that a good night's rest helps us stay healthy. After we sleep for 7 or 8 hours in bed and {#blank#}1{#/blank#} 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 {#blank#}2{#/blank#}  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 {#blank#}3{#/blank#} 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  {#blank#}4{#/blank#} the age of 65. Doctors say that napping for about an hour may be too  {#blank#}5{#/blank#} for young and healthy people. And they believe that half an hour is enough to {#blank#}6{#/blank#} young and healthy people from feeling tired. By doing so, {#blank#}7{#/blank#} will help them stay awake.

    Doctors also say, “If you have trouble falling asleep at {#blank#}8{#/blank#} , take a daytime nap for less than 45 minutes and don't nap after 3 p.m. in the afternoon.