We have known for a long time that flowers of different plants open and close at different time of day. Yet no one really understands why flowers open and close like this at special times. It is not as simple as we might think, as new experiments(实验) have shown. In one experiment, flowers were kept in darkness. We might expect that the flowers, without any information about the time of the day, did not open as they usually do. In fact, they continued to open at their usual time. This shows that they have some mysterious (神秘的) way of knowing the time.

    Their sense of time does not depend on information from the outside world; it is, so to speak, inside them, a kind of “inner clock”. This discovery may not seem to be very important. However, it was later found that not just plants but also animals including man have this “inner clock”which controls(控制) working of their bodies and their activities.

    Human beings, then, are also controlled by this mysterious power. Whether we wish it or not, it affects such things in our life as our need for sleep, our need for food. And our ability to concentrate(集中).

    There will be a kind of new cars in the future. People will like this kind of small cars better than the big ones. The car is as small as a bike. But it can carry two people in it. Everybody can drive it easily, just like riding a bike. Even children and old people can drive them to schools or parks.

    If everyone drives such cars in the future, there will be less pollution in the air. There will be more space for all the cars in cities, and there will also be more space for people to walk in the streets.

    The little cars of the future will cost less money to buy and to drive. These little cars can go only 65 kilometers an hour, so driving will be safer. The cars of the future will be fine for going around the city, but they will not be useful for a long trip.

    This kind of cars can save a lot of gas. They will go 450 kilometers, then they have to stop for more gas. They are nice cars, aren't they?

    Each year more than2,500 people die and 12,600 are injured in home fires just in the UnitedStates, with direct property(财产) lossbecause of home fires at about $7.3 billion every year. Every day Americansexperience tile horror(惨状) of fires, but most people don'tunderstand fires.

    To protect yourself, itis important to learn something about home fires.

    In less than 30 secondsa small flame can get completely out of control and turn into a major fire. Itonly takes minutes for thick black smoke to fill a house or for it to be inflames. Most deadly fires occur in the home when people are asleep, lf yourealize a fire, you won't have time to take valuables because the fire spreadstoo quickly and the smoke is too thick. The fire uses up the oxygen you needand produces smoke and poisonous(有毒的) gases that kill. Breathing even small amounts of smoke and toxicgases can make you tired and sleepy, and short of breath. The smoke can causeyou to be a deep sleeper before the flames reach your door. You may not wake upin time to escape.

    Room temperatures in afire can be 100 degrees at floor level and rise to 600 degrees at eye level.Breathing in this super-hot air will burn your lungs. It can melt clothes toyour skin. In five minutes, a mom can get so hot that everything in it startsto burn at once.

    Fires are bright atfirst, but quickly produce black smoke and complete darkness. If you wake up toa fire you may be blinded, confused about where you are or which direction you shouldgo in and unable to find your way around the home you've lived in for years.

    Only when we know thetrue nature of fires can we prepare our families and ourselves.

    Thousands of years ago, people couldn't live for long. Most people only lived to be twenty-five or thirty years old. 20% of people died before they were twelvemonths old and another 30% could not live to be five years old.

    Today, people can live much longer. One reason is that the water we drink is cleaner. Clean water does not cause diseases（疾病）. Besides, medical treatment is better today. More and more people live to be over eighty.

    Women often live longer than men. For example, in Japan, women usually can live to be eighty-five, but men can only live to be eighty.

    In the future, people will probably live longer than today. Here are many things we can do to help people live longer. For example, we can make sure that everyone has enough medicine to fight against diseases. Also, it is necessary for everyone to have enough to eat. Today many people die because they do not have enough food.

    Squirrels (松鼠) are getting ready for winter. They are looking for nuts and seeds, digging holes in the ground or finding holes in trees. That's where they store the food they will need during the coming months, when the weather is cold and sometimes snowy.

    Squirrels spend a lot of time in trees, which are like restaurants for them. Among their favorite things to eat are nuts and other parts of trees, like tender buds (花苞).

    Squirrels may also eat corn, insects and other animals. And, as anyone who has a bird knows, squirrels love bird food!

    Squirrels stay active all winter, so they need plenty of food to help keep up their energy. Squirrels tend to bury food underground, piece by piece. Some squirrels may gather food into piles that they put at the base of trees or bury underground.

    When they need food, squirrels use their memory and smell to help them find what they buried. Sometimes, you'll even see them digging through the snow.

    Squirrels make nests in trees. Some squirrels spend much of the winter in underground tunnels (地道), where it is warmer.

    When spring comes, squirrels change their eating habits to new plant growth, like buds and leaves. Sometimes they forget to dig up all their buried nuts.

    That's why you'll sometimes find a little tree growing in a place where neither you nor your family planted it. It must have been the squirrels.

    How green are you? Do you know how to be green? We all need a healthy environment, but we produce waste every day and it is harmful to our environment. Though we are young, we can still do something to help. Here are some ideas for you.

    Reduce

    Reduce means "use less" .Don't waste things. This saves money and reduces pollution. Before we buy something new, think whether it is really necessary— or maybe the old one is still useful.

    Reuse

    Reuse means "use again" .When we buy things, make sure that they can last a long time. When something is broken, we should repair it instead of throwing it away and buying a new one. Don't use a paper cup or a paper bag. It's better to use a china(瓷) cup and a lunch box because you can use them again.

    Recycle

    Recycle means "change things into something else" .Though it takes energy to change something into something else, it's better than throwing things away or burning them.

    So please remember these three words: reduce, reuse and recycle.