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    For many years, scientists have said that the earth is getting warmer. Now they have found something new—hot cities! In the southern US, they have found that cities become very hot in summer. For example, the city of Atlanta in Georgia has roof(屋顶) temperature of up to 50^oC while it is 27℃ in the streets! At night, the outside of buildings stays so hot that the heat of the city causes storms over the city!

    China also has the same kind of problems. Every year more farmland is used for factories or offices. More housing is needed, too. As people become richer, they buy more cars. New roads are needed and new car parks are built in the city centers. This all makes cities hotter.

    It isn't easy to change the situation. City planners say that we should plant more trees in the middle of cities. Every new street should have trees on both sides, they say. Trees make the temperature lower, so we should have more trees in our parks and squares. We should also paint our roofs white. If we do this, they do not become so hot. Every roof in a hot and sunny country should have solar(太阳的) roof panels. The electricity from these can be used to run the air conditioners (空调)in the buildings.

    People continue to cut down forests around the cities. This makes the problem worse. Cities are growing faster and faster. By the year 2025, four fifths(五分之四) of the population will be living in cities. If we go on like this, there will not be enough farmland to feed everyone in the world.

    The world's forests become smaller and smaller. People are still cutting down the trees. Why is this happening? There are two reasons—land and wood. People need land for animals and crops. And people want wood. Japan, Europe and North American need wood. There, it is used for buildings or it is made into furniture.

    But most places from the forests are not good for animals or crops. The soil (土壤) in the forests is very thin. When trees are cut down, the soil is washed away by the rain or the wind. Soon there is nothing but sand. Then more land will be needed and more trees will be cut down.

    Animals are natural resources that people have wasted all through our history. Animals have been killed for their fur and feathers, for food, for sports, and simply because they were in the way. Thousands of kinds of animals have disappeared from the Earth forever. Hundreds of animals are on the danger list today. About 170 kinds in the United States alone are considered in danger. Why should people care? Because we need animals, and because once they are gone, there will never be any more. Animals are more than just beautiful or interesting. They are more than just a source of food. Every animal has its place in the balance of nature. Destroying one kind of animal can create many problems. For example, when farmers killed large numbers of hawks, the farmers' stores of corn and grain were destroyed by rats and mice. Why? Because hawks eat rats and mice, with no hawks to keep down their numbers, the rats and mice multiplied quickly.

    Luckily, some people are working to help save the animals. Some groups raise money to let people know about the problem. And they try to get the governments to pass laws protecting animals in danger. Quite a few countries have passed laws. These laws forbid the killing of any animal or plant on the danger list. Slowly, the number of some animals in danger is growing.

    Every year on April 22, People all over the world celebrate Earth Day. It is a time to work to keep our earth clean. People plan projects to clean up the land, air and water.

    U.S. Senator Gaylord Nelson first thought of the idea for Earth Day in 1962 when he saw polluted rivers and cities with smoke. He needed to get support from Americans to clean up the earth. Finally, on April 22, 1970, 20 million Americans celebrated the first Earth Day! Now many countries around the world celebrate it, and you can, too.

    How can you celebrate Earth Day? Here are a few ideas:

    Join a clean-up project-Clean up your street or a favorite beach.

    Save energy-Turn off the lights when you leave a room, and use public transportation.

    Use less water.

    Reduce(减少)/ Reuse/ Recycle ― Practice the three Rs: First, reduce how much you use. Then reuse or recycle what you can.

    You can make a difference on Earth Day and every day!

    What should you do if there's an earthquake at school? How can you protect yourself when you are caught in a stampede(踩踏)?March 28, 2016 provided you with a good chance to learn about safety.

    This day was called the National Day of Education on the Safety of Elementary and Middle School Students(NDESEMSS)(全国中小学生安全教育日). The theme of the day was to give students more knowledge about safety and make sure their lives are safe.

    A survey done by the China Youth and Children Research Center showed that school accidents kill more elementary and middle school students than anything else. The main accidents come from stampedes, earthquakes, fires and sports injuries(伤害).

    What can we do to keep ourselves safe? Staying calm is the first and most important rule when facing accidents. But different accidents have different self-protection advice.

    A stampede is possible anywhere. The larger a crowd gets, the more likely stampedes become. When students around you begin to push, stand still and try to hold onto something, or stay in a corner until the crowd leaves. If you fall down in a moving crowd, cover your head with both hands. Lean to(偏向) one side, curl up(蜷缩) your body and bend your legs.

    Earthquakes are common natural disasters(灾难). When you feel the ground shake, drop down, take cover under a desk and hold on. You should stay indoors until the shaking stops. If you are outdoors, don't stay near buildings, trees or power lines.

    When there's a fire, follow the teachers' instructions, leave the classroom quickly and use a piece of wet cloth to cover your mouth and nose so that you don't breathe in smoke.