The bicycle is one of the simplest and most useful inventions in the 1 world. What is the most surprising is that it was not invented earlier, although the great inventor Leonardo da Vinci had drawn pictures for bicycles and also for flying machines and some other things. Those things were not produced until long after he died.

    A person riding a bicycle uses very little energy to make the bicycle move, and there is no pollution at all when you are riding. In Chengdu, a lot of people rode bicycles to I work twenty years ago. But cars instead of them now. Even so in developed countries, most people do not travel to work by bicycle. It is not because the bicycles 9 are expensive or people feel tired if they ride to work. It is because the number of cars on the roads is becoming larger. It certainly becomes more dangerous to ride a bicycle. As a result, more people put their bicycles away and go to work in their cars. And in this way, the traffic is very crowded when people go to work by car in the morning and go home after work, the situation is becoming worse and worse.

    Perhaps the best way to make riding safer and more popular is to create paths only for bicycles, and to make it so difficult and expensive for drivers to take their cars into the city that they will go back to use their bicycles. There has been a special way for bicycles on the road in Chengdu now. I think more and more people will return to ride bicycles to go to work. The air of cities will be much fresher. The sky will be a lot bluer. The people will live much happier lives.

    The giant panda is unknown as the national treasure of China. The panda was a kind of common animal in China long . However, for some reasons, too many of them have been killed. So the number of them is quickly.

    At present people are taking action to save pandas. People want to find a home for them, and recently, they have a nature park for them in Sichuan Province, which is "the Pandas’ Home". There pandas can enjoy their lives happily. There is a bamboo forest near "the Pandas' Home", so the pandas can find bamboos which they like to eat very much.

    Because pandas are well protected now, the number of them is increasing every year. We hope that one day we will have enough pandas to set them and let them live in the wild again.

    Pandas are good friends of man. Man should try to protect them and let them live in the way they like!

    Do you know why different animals or pests (害虫) have their special colors? Colors in them seem to be used mainly to protect themselves.

    Some birds like eating locusts. But birds cannot easily catch them. Why? It is because locusts change their colors together with the change of the colors of crops. When crops are green, locusts look green. But as the harvest time comes locusts change to the same brown color as crops have. Some other pests with different colors from plants are easily found and caught by others. So they have to hide themselves for lives and appear only at night.

    If you study the animal life, you'll find the main use of colors is protecting them. Bears(熊), lions and other animals move quietly through forests. They cannot be seen by hunters. This is because they have the colors much like the trees.

    Have you ever noticed an even strange cat? A kind of fish in the Sea can send out a kind of very black liquid(液体) when it faces danger. While the liquid spreads over , the enemies (敌人)can not find it. And it quickly swims away. So it has lived up to now though it isn't strong at all.