Color is everywhere in lives. But what does color mean? Why are people more relaxed in green rooms? Why do people do their best in blue gyms? That's the magic of color!

    Scientists from the US did an experiment. They asked two people to go into two different rooms. One went into a room painted in pink, and the other went into a blue room. They had to stay in the rooms for one hour. But they had to guess the time, because they didn't have a watch or any other thing to see the time. In the end, the person in the pink room came out in about 40 to 50 minutes. The person in the blue room came out after 70 to 80 minutes.

    The results show that color can change people's feelings about time. Warm colors make people feel that time is going faster than cool colors.

    No Car Day was first started by 34 cities in France on September 22, 1998. It was started to protect the environment. By now, more than 1,000 cities around the world have had a No Car Day.

    The first No Car Day in China was in Chengdu in 2001. Other cities, including Taipei, Shanghai and Wuhan, also support the day.

    In Beijing, more and more people are joining the campaign. It asks drivers to leave their cars at home for one day each month and walk or ride a bike to work. It also calls on Beijingers not to use cars on June 5(World Environment Day). The slogan for the day is, “If we drive for one less day, we can have one more nice day.”

    So far, more than 200,000 drivers have shown their support. “We can't control the weather, but we can choose not to drive,” said Wu Zonghua, a car club chairman. Beijing is trying to have 238 blue sky days this year. In the first quarter of 2012, Beijing only had 52 blue sky days. This was 11 days less than the number for the same period the year before. Much of the dust comes from the desert, but cars cause most of the air pollution. We must do more for No Car Day.

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    Imagine the situation. You are driving along a desert or on a mountain. You have no idea where you are. You passed the last house two hours ago. Then your car breaks down. It is night and it is cold. You have no mobile phone. What do you do? Well, next time take a GPS with you. This invention may be able to help you. It is a device(装置) which uses satellites (卫星) to find the user's position(位置). It can find your position to within 20 metres. A GPS cannot start your car, but at least you will know where you are.

    GPS, which means Global Positioning System, is a small radio receiver. It looks like a mobile phone. You can hold it in your hand, or put in your pocket. It is sometimes put into a watch or a telephone. We also find GPS devices in cars, planes, or boats. Some of these devices have electronic maps, so you know where you are. For example, in a city they can tell you the name of the street.

    There are three parts to the Global Positioning System. The first part is the receiver. You can hold it in your hand, or have it fixed into your car, plane, etc. The second part is a group of satellites orbiting the Earth. The receiver contacts at least four of the satellites and calculates(计算) its position. The third part of the system is a network of ground stations. They are all over the world. They control the satellites and make sure they are working well.

    Some people think that in the future the GPS will be as common as the mobile. They are becoming cheaper and more and more accurate(精确的). There are also new uses for the GPS. Perhaps they will become like watches. Everyone will have one and you will never be lost again.

    We need animals. Every animal has its place in the balance(平衡) of nature. We should try to help save the animals.

    Some people think zoos are good places. The zoos give the animals the comfortable and safe living places. If the animals get hurt or ill, people will take care of them. The zoo is a good place to know the rules in the wild world. We can be much closer to nature. We can know more about the animals in the zoos by watching, listening even smelling instead of just looking at the pictures in books.

    Some people don't think animals feel happy in the zoos. Animals like pandas, wolves and bears usually live in the wild. They play and find food by themselves. They are free and happy in the wild. If they are in the zoos, food is enough and rooms are comfortable. They do not need to do their best to find food to eat or places to stay in. They just walk around, sleep day and night, but they are not free at all.

    I think we should build national parks as wild life nature reserves to protect animals. If we do nothing, animals will get fewer and fewer.

    Every day there is less and less space on Earth for rubbish. Yet every day we make more and more rubbish. What can we do? We can recycle some of our rubbish. Recycling means that the rubbish will be made into something that can be used again.

    Recycling helps Earth. And it saves space in rubbish dumps. Half of everything that we put into landfills could be recycled instead. In fact, most things made of paper, metal, glass and plastic can be recycled.

    Paper can be broken into small pieces and made into new paper. Steel and aluminum cans(金属雄)can be melted down(熔化)and made into new cans. The same is true of glass bottles. This can be done over and over again. Recycling doesn't take as much energy as making these things the first time. So we can use less of Earth's fuel resources.

    Plastic can be melted down, too. Then it can be formed into park benches, playgrounds and so on. Some people call plastic the "wood" of the future. Things made of plastic will last about 400 years-even if they stay outside in the weather. No wood can do that!