Where does the wind come from? What makes the wind move(移动) all the time? Scientists tell us that it is the sun. That makes air move, and makes it blow(吹). When the sun shines on the earth, it makes the earth hot. Then the earth makes the air hot. When the air becomes hotter, it also becomes lighter(更轻). The light air goes up. Cool air comes into take the place of（代替） the hot air. The hot light air goes up higher and higher until it becomes cool. Then it comes down again, and then the earth makes it hot again, and it has to go up. When the air move, it has wind.

D

    Are you nervous? Maybe you should sit in a blue room. Are you always cold? Maybe you should sit in a room painted in a "warm colour" such as soft orange. Are you often sad? Maybe you should sit in a yellow room. Some researchers believe that colour has the power to influence our feelings. They believe that colours affect(影响)everyone in the same way.

    One study was in a workplace. The researchers painted heavy boxes white and light boxes black. They want to see how colour affected the workers' feelings. Which boxes do you think were more difficult to lift? The heavy white ones? No. The white boxes were heavier but they looked light. The researchers think that this is because light colours seem light.

    Another study was at school. Researchers at the University of Alberta in Edmonton, Canada, studied children with behaviour problems in their classroom. When the walls were brown and yellow, the children's heart rate went up and they were over-active. However, when the walls were dark blue, the children's heart rate was slower and the children were much calmer. If this is true, we can think carefully about the colours around them--not just in our homes, but also in offices, in schools, in hospitals, in gyms, in museums, in restaurants and even in prisons.

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    Sharks(鲨鱼) are the most frightening animals in the sea. Sometimes we can see sharks swimming in the sea around Hong Kong. People put nets around some beaches to protect swimmers. When there is a "shark's flag", people must stay on the beach. It will be too late if a shark can swim sixty kilometres an hour to you.

    There are 30 kinds of sharks and 25 kinds of them are dangerous. The whale sharks are, very big. They can grow to 18 metres long, but they are not dangerous to people. The jaws(大白鲨) and the tiger sharks are the most dangerous kinds of sharks.

    Do you know all sharks must keep swimming, or they will go down?

All sharks can feel everything that happens around them. We must keep calm and don't make any noise when a shark is swimming near you.

    If a shark loses a tooth, a new one will grow out very quickly. So sharks always have many sharp teeth.

    The world has a plastics problem. And not just with bottles. Straws (吸管), toothbrushes, toys—all kinds of plastics are placed in landfills. There are 5 billion tons of plastic waste in the world. Landfills have a large part of it. By 2050, they could have 13 billion tons.

    Much of plastic rubbish finds its way into the ocean. Scientists say 165 million tons of plastic pieces are floating around out there. And most plastic won't disappear itself. It will remain in the ocean forever. Whales get caught in plastic fishing nets. Birds die because of eating plastic straws and bottle caps. It endangers ocean life. Plastic rubbish even ends up in the food we eat.

    Governments are realizing that recycling may not be enough. They are taking more actions. Though it is hard work, it is still a solvable problem. In Britain, people are not allowed to use plastic bags except in hospitals. Scotland and several coastal cities in the US stop people from using plastic straws as well. The US alone throws away some 500 million plastic straws a day. That's enough to circle the Earth twice. "Saying no to a plastic straw is an easy way to make a big difference," Diana Lofflin who started www.strawfree.org said. "'Do we really want to pass on to our children a world harmed by plastic?"

    People have found some tasty ways to reduce waste. A company in India made the first-ever spoon that people can eat. You don't have to eat the spoon. You can throw it away. It decomposes (分解) in just a few days. David Edwards, a scientist at Harvard University, designed an eatable bag which can protect the food or drink inside. It is a delicious replacement for plastic ones.

    Did you know that each day one person in the USA throws away 4.4 pounds of rubbish? Almost every month, we throw away our own rubbish in packaging alone. Packaging (including boxes, bags, etc.) comes to our homes with the things we have bought. Several weeks ago, the TV news said that in a city in Italy tons of rubbish were piled up in the streets, and the smell was rather terrible. What can we do to help? We should get to know the following Rs.

    Reduce To reduce means to make less rubbish. That is one of the first things we all should do for the environment. Reduce your rubbish by doing things like packing your lunch in reusable containers(可再利用的容器), taking smaller portions(份) at dinner so you don't waste food when you have had enough, writing on both sides of paper, and using less water when taking a shower.

    Reuse to reuse is to use things again. Think about the bags you get from the shop. They can be reused to carry your lunch, to hold your rubbish, or to collect used cans. You can even take them back to the school next time to carry your things instead of getting a new bag!

    Recycle(回收利用) Recycling is an important part of keeping our planet clean and green. It can also save energy. Be sure that you don't throw things in the rubbish bins that can be recycled to make something else Paper, plastic, cans and bottles can all be recycled. But food, electrical waste and mobile phones cant. When you are not sure whether something can be recycled, go to your parents and teachers for advice.

Follow the three Rs, and every one of us can do something to save the Earth. It is also the best way to save ourselves.