Sleep is something we all do. But some people need to sleep more than others. Babies sleep most of the time. Children in school sleep about ten to twelve hours a night. Most adults sleep only seven or eight hours. {#blank#}1{#/blank#}

    All parts of our bodies have to rest after they work.. Our arms need a rest after we lift heavy thing, When we run fast, our legs work hard. They get tired. We have to rest them. Our brains work hard, too. {#blank#}2{#/blank#}. We can sit quite still and rest our arms and legs. But our brains aren't resting. They go right on thinking as long as we are awake.

    Our brains slow down a bit when we sleep and dream. {#blank#}3{#/blank#} Instead of thinking wide-awake thoughts, our brains make up dreams. Some dreams are very pleasing. Some are not. Most of the time we forget them when we wake up.

    Scientists have tried to find out what would happen if people were not allowed to sleep. They asked some people not to go to bed. The people stayed up all night and all the next day. They stayed up the next night too, and the day after. They played games, but they made mistakes. They forgot things. {#blank#}4{#/blank#}

    The people grew rude and mean. They became angry with their friends. Finally they were too tired to stand up. When they sat down, they fell asleep.

    Scientists have found that if people are not allowed to sleep and to dream, they act in an unusual way. {#blank#}5{#/blank#} But we do know that we need it to stay well. So tonight have a good sleep. Lie down under the covers. Shut your eyes. Let your thoughts wander. Soon you'll stop thinking. You'll be asleep.

A. It was hard for their tired brains to work.

B. When we are awake, they help us pay attention to the world around us.

C. But babies, children, and adults — all of us need to have our sleep.

D. Good sleep helps to improve one's memory.

E. No one knows why sleep is so good for us.

F. But even as we sleep our brains are doing some work.

G. Of course you will have a good sleep.

    When was the last time you relied on an old-fashioned map to figure out the route to an unfamiliar place? For many, the GPS has revolutionized navigation, making a paper map almost obsolete? So how has this piece of technology developed over its 26 years of existence? On February 14,1989,the first satellite in the US Global Positioning System was sent into space from Cape Canaveral, beginning the start of one of the wonders of the modern world.

    GPS stands for Global Positioning System, which is made of a network of around 30 satellites that move around the earth. The system uses a process called trilateration to find out one's position. By measuring the time it takes for the signal to reach one satellite, the GPS can determine your distance from the satellite, creating a sphere(范围) of possible locations. Measuring your distance from at least three satellites will narrow your location to the place where the three spheres cross one another, to the accuracy(精确) of about less than 1 meter!

    The GPS was first invented during the Cold War by the United States Department of Defense. In 1960, the first system, which was made of just five satellites, was put into place. It was initially created for strictly military(军事的) use; however, in 1983, as a result of faulty navigation technology, a Korean passenger plane mistakenly flew into USSR territory(苏联领土) and was shot down. In order to prevent such bad events, American President Ronald Reagan allowed civilian(民用的) use of the GPS.

    Over the next ten years, the system's accuracy improved as the network was increased to 24 satellites. And during the first Persian Gulf War, the new GPS was finally used by the military. Now scientists use the technology to track animals to better understand their movement and behavior. Parents who may be worried about their children can also use GPS technology to track them.

    British scientists have discovered the willow trees planted at an angle could increase sugars for biofuel production.

    Willow is a fast-growing species. It is already used to produce fuels for the renewable heating and power market. In future it could also help to produce biofuel to power vehicles. It has been known that when willows growing in the wild are blown sideways, they tend to produce more sugars. But for a while it has not been known why this happens.

    Researchers at Imperial College London, led by Dr Nicholas Brereton and Dr Michael Ray of the Department of Life Sciences, have now solved the mystery. When the tree is blown sideways, its genes (基因) produce large numbers of sugar molecules (分子) to straighten the tree upwards.

    “This is an important breakthrough. Our study now shows that natural genetic changes are related to these differences. And this could well be the key to unlocking the future for green energy from willow,” said Dr Brereton.

    The research was carried out under lab conditions. The willows were grown at an angle of 45 degrees. They were compared to willows which grow naturally straight upwards. The team then looked for the same effect among the willows growing on the Isle of Orkney where strong winds cause the trees to bend at extreme angles. They discovered that the Orkney trees produce five times the amount of sugars found in willows grown in sheltered conditions.

    Willow is widely planted across the UK. The results show that biofuel crops such as willows could be grown in climatically changeable conditions where chances of growing food crops are limited.

    The study is published in Biotechnology for Biofuels.

    It is important to know another language and how to communicate without words when you are in another country. Before saying anything, people communicate with each other by using gestures(手势). However, many gestures have different meanings, or no meaning at all, in different parts of the world.

    In the United States, nodding your head up and down means "yes", while in some parts of Greece and Turkey, it means "no". In the southeast of Asia, it is a polite way of saying "I heard you".

    Today in the USA, when someone puts his thumb up, it means "Everything is all right." However, in Greece it is bad. Also putting your clasped(紧握的)hands up above your head means "I am the winner." It is the sign which players often make. In Russia it is the sign of friendship.

    In the USA, holding your hand up with the thumb and index finger(食指), and the other three straight means "Everything is OK." In France, it means "You are worth nothing."

    It is also important to make eye communication. If you look down when talking to an American, he or she may feel that you are shy, or you are trying to hide something.

Besides these, you should also know there are some topics that cannot be talked about, such as age, weight and marriage. You can talk about the weather, work, sports, food, where one lives and news of the day.

    Breakfast is not only the most important meal of the day, but also the most neglected. Common reasons for not eating breakfast include lack of time, not feeling hungry, traditional dislike for breakfast, and dieting.

    Breakfast simply means "break the fast". Your body spends at least 6 to 12 hours each night in a fasting state. In the morning your body needs energy for the day's work ahead.

    A good breakfast should provide up to 1/3 of your total calories needs for the day. On average(平均)we eat 400 less calories for breakfast than for dinner. If breakfast doesn't attract you in the morning, try eating a lighter for the breakfast in the morning.

    If you aren't hungry in the morning, start with something small like juice or toast or have a nutritious mid-morning snack alter when you are hungry.

    So, you say you're on a diet. Some people fear eating breakfast will make them hungrier during the day and they will eat more. It is true that eating breakfast is likely to make you eat more. That's because your body is working all day long, in fact, you are probably not.

    Not eating breakfast can also cause you to overeat, since a fall in blood sugar often makes you feel very hungry later. To make matters worse, since your body is in a slowed state it will not be able to burn those extra calories very quickly. If you feed your body healthy snacks and meals through the day, you are less likely to become hungry and fill yourself as soon as you begin to eat. Since breakfast is the first and most important meal of the day, choosing the right fuel is important. The best breakfast foods are fruits, juice, lean meat, and grain products such as bread, rice, noodles and cereals(谷物).

    Taking your pulse during physical activity allows you to measure how hard you are exercising. You should exercise to stay within your target heart range.

    Increasing your heart rate is a key part of exercise but it is important that your heart rate is not too high or too low. If you are a beginner, you should also be able to breathe comfortably while exercising. This will ensure that you are exercising at a level that is safe and effective for your body.

    The chart below illustrates target heart rate ranges for exercise based on the maximal heart rate for selected ages. Here are the steps for using the chart: