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    Thousands of bats(蝙蝠)in the Northeast are dying, and no one knows why. Scientists are conducting investigations(开展调查) to find out the cause and stop the spread of deaths, which have been most heavily reported in New York, Vermont and Massachusetts.

    "Most bat researchers agree that this is the most serious threat to bats they have ever seen, " says Alan Hicks, a bat expert who works in the New York Department of Environmental Conservation.

    There are few clues about the cause of the deaths. Bats are easy to catch the contagious disease(传染病) because they hibernate(冬眠) together. In some caves, there are 300 bats per square foot. Environmental officials are asking people to stay out of bat caves to avoid spreading the mysterious(神秘的) sickness while they are working to find out what it is.

    Most American children eat potatoes. But many children don't know what of the potato is the best food. Take a knife and cut from the middle of the potato a piece as thin as paper. I hold the piece between your eyes and light. You will see that the potato has skin(皮), an outside rim(边缘)and an inside part. The outside rim which is right under the skin of the potato, is the most valuable part of all. But this is often thrown away with the skin. Even the skin itself is better for food than the inside. When eating a cooked potato, if you choose the inside and leave the outside, you are throwing the best part of it. If you can't cat the whole potato, eat the outside rim first and leave the inside part.

    Thanks to the Earth, we have fresh air to breathe, clean water to drink and warm sunshine to enjoy. But it seems that we haven't realized that the Earth is facing many environmental challenges and it is getting "sick".

    Scientists say that of all the environmental challenges, climate (气候) change is the biggest one. The temperature on the Earth has risen by more than 0. 5C since 1992. Cities like Singapore and Tokyo that are at low altitudes (海拔) may be covered by the ocean (海洋) in the future.

    But this is not the only problem people are facing. Since 1992, the human population has grown by 2 billion, while the population of all other animals has dropped by nearly 30 percent. At the same time, water pollution has become serious. We are also facing problems like light pollution, noise pollution and some other pollution.

    However, we have made some progress in saving the Earth. For example, we stop using harmful materials to make the hole in the ozone layer (臭氧层) smaller to slow the rise of the temperature. We do a lot of work to help the animals in danger, or more than two-thirds of the worlds wild animals may disappear (消失) by the end of 2020.

    "The progress shows that we can make good changes when we act wisely, "scientists say, "we must take action to protect the environment, or it will be worse."

     The world itself is becoming much smaller by using modern traffic and morden communication means (工具). Life today is much easier than it was hundreds of years ago, but it has brought new problems. One of the biggest problems is pollution. To pollute means to make things dirty. Pollution comes in many ways. We see it, smell it, drink it and even heart it.

    Man has been polluting the earth. The more people have, the more pollution becomes. Many years ago, the problem was nor so serious because there were not so many people. When the land was used up or the river was dirty in one place, man moved to another place. But this is no longer true.

    Man is now slowly polluting the whole world.

    Air pollution is still the most serious. It's bad for all living things in the world, but it is not the only one kind of pollution, Water pollution kills our fish and pollutes our drinking water. Noise pollution makes us angry more easily.

    Many countries are making rules to fight pollution. They stop people from burning coal in houses and factories in the city, and from putting dirty smoke into the air. Pollution by sulfur dioxide (So₂) is now the most dangerous kind of air pollution. It is caused by heavy traffic. We are sure that if there are fewer people driving, there will be less air pollution.

    The earth is our home. We must take care of it. That means keeping the land, water and air clean. And we must pay attention to the rise in pollution at the same time.