Junior school students in Harbin，Heilongjiang, had a "long weekend". They had four days off from Oct. 19-22. It was not for any festival, but was caused by serious smog.
    The smog was caused by high levels of PM 2.5 in the air.
    PM 2.5 is small particles（微粒） of pollution in the air with a diameter （直径） of 2.5 micrometers or less. Waste gas from cars and factories is the biggest cause of PM 2.5 pollution.  On Oct. 17, the World Health Organization named air pollution a cause of cancer.
    To better protect children, cities are taking action.
    On Oct. 21, Harbin Education Bureau decided to close primary and junior high schools for two days.
    Beijing started a program on Oct. 22 which has a warning system with four levels. The red warning is the highest warning level. It means that the next three days will see serious pollution.
    When a red warning is issued（发布）, schools will close.
    If there's pollution that's not as serious, the Beijing Commission of Education will ask schools to stop PE classes and outdoor activities.
How will students be informed?
    "First, the Commission of Education will inform schools online," Ye Yan, head of Beijing Shijingshanqu Experimental Primary School, told Beijing Times. "Then teachers will text students' parents."
    Will the days off affect the study plan?
    "Missing school days will be made up during the summer or winter vacations,"  said Wang Hao, a physical education teacher in Beijing Chaoyang district.
    For students in Harbin who had the long weekend, they would go to school on the next two Saturdays.

    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 does harm to our environment. Though we are young, we can still do something to help. In fact, even the simplest everyday activities can make a real difference to the environment. Here are some ideas for you.

    Reduce

    Reduce means “use less”. Don't waste things. This saves money and reduces pollution and waste going into the environment. Before we buy something new, think whether it is really necessary—or maybe the old one will be just as good! When we do buy things, choose local products if possible, and try not to buy too many things from abroad.

    Reuse

    Reuse means “use again”. Use things for as long as possible. When we buy things, make sure that they last a long time. We should look after them so that they will last, and we should repair them if we can instead of throwing them away and buying new ones. Don't use a paper cup or a paper bag. It's better to use a china cup and a lunch box because you can use them again.

    Recycle

    Recycle means “change things into something else”. Though it takes energy(精力) to change something into something else, it's better than throwing things away or burning them. Find out what can be recycled in your neighborhood and take part in recycling programmes. We should also buy products made from recycled materials, such as recycled paper, to help save trees.

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

A

    Air pollution is one of the most common types of pollution in the world nowadays. It is quite serious in many places, especially in big cities. It can do great harm to our environment such as making the earth warmer, causing acid rain or destroying the ozone layer. As for human beings, air pollution causes all kinds of breathing problems.

    There are several reasons for air pollution. Firstly, many cities have a lot of factories and there we need to make food, clothing and other things. Every year these factories pour millions of tons of smog into air. Secondly, power factories can also give out harmful air. For example, in 1986 there was a bad accident at a nuclear power station in Russia. A cloud of radiation crossed the whole Europe. It is said that 125,000 people died in Russia as a result of illnesses caused by this accident. Thirdly, there are more cars in cities now. Once they are out in the streets, they will take in fresh air and give out dirty gas. Besides, smoking cigarettes also makes air pollution worse as will as damaging(损害) our health.  

    A hundred years ago, most people thought that human beings would never fly. And the idea of flying seemed crazy and dangerous. But as a new world full of new inventions（发明物）came, everyone was trying to break the old thoughts. So many inventors, like Orville and Wilbur Wright, tried to make a flying thing.

    Most plane inventors at that time were impulsive. They would think of an idea, make a plane as quickly as they could, and then try to fly it as soon as possible. All of them had the same result they took their planes home and they had no idea why they didn't work.

    However, the Wright brothers were much smarter inventors. They tested their ideas in smaller or safer ones before making a real plane. For example, the Wright brothers made a wind tunnel(隧道)to compare(比较)wing shape ideas. They also flew lots of kites to test their ideas. They studied the way birds fly through the air and tried to learn something from it when making their models. Finally, the Wright brothers felt they were ready to test their planes, but they needed to find the right place. They knew the right place to test their planes after writing to the US Weather Bureau for help. At last on December 17th, 1903, Orville and Wilbur tested the plane and they made it.

    The plane flied for twelve seconds and it traveled just 120 feet, but Orville and Wilbur were very happy. Their plane really worked! By the end of the day, both brothers had great successful flights(飞行), with Wilbur having a record of 852 feet in 59 seconds.

    Animals grow up（成长） in different ways. Some newborn（初生的） animals are helpless but their mothers protect them. A newborn kangaroo is very small. It is only a few centimeters（cm）long. It closes its eyes and doesn't have hair. It stays safe in its mother's pouch（育儿袋）for a long time.

    A newborn monkey can not walk. Its mother carries it everywhere.

    Other baby animals can walk soon after they're born. They learn to run with their mothers when danger is near. A baby zebra can run, an hour after it is born.

    Some baby animals are born in a place that is safe. Baby wolves are usually born in big holes with little light. Other baby animals are born in the open. A baby elephant is often born on open land.

    Animals, including insects, do not have a language like ours. They do not talk to each other in words and sentences. But if we watch them, we can see that they do have ways of communicating with each other.

    Can you see the rabbit's tail which is moving up and down? When rabbits see this white tail moving up and down, they run too. They know that there is danger. The rabbit has told them something without making a sound. It has done this by using its body language.

    Many other animals use this kind of language. When a cobra is angry, it raises its hood and makes itself look fierce. This warns other animals. When a bee has found some food, it goes back to its home. It cannot tell the other bees where the food is by speaking to them, but it does a little dance in the air. This tells the bees where the food is.

    Some animals say things by making sounds. A dog barks, for example, when a stranger comes near. A cat purrs when pleased. Some birds make several different sounds, each with its own meaning. Sometimes we human beings speak in the same way. We make sounds like "Oh" or "Ah!" when we are frightened or pleased or when we drop something on our toes.

    But we have something that no animals have—a large number of words that have the meanings of things, actions, feelings or ideas. We are able to give each other all kinds of different information in words and sentences, which no other animals can do. No other animals have so wonderful a language as we have.