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    高二英语上期期末阅读理解训练题(4)
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    Hole in the Sky

    Earth's ozone has a very important task: protecting us from the sun. While we do need the sun's energy, its powerful ultraviolet rays would be harmful to earth if they hit our planet with their full impact. The crucial ozone filters(过滤) the sun's radiation, making the layer's presence absolutely vital for our survival.

    To understand the possible effects of losing the ozone, recall the last time you had sunburn. This burning of the skin is caused by ultraviolet (UV) light from the sun. The sun's radiation also causes cancer, weakens our immune systems, and has other harmful effects. Fortunately, the ozone absorbs almost all of the harmful UV radiation. Ozone forms when oxygen molecules (O2) are split by ultraviolet radiation into two separate oxygen atoms (O), and these single oxygen atoms can collide with oxygen molecules. The result is 03--ozone!
    Ozone is a form of oxygen that unfortunately can be destroyed easily by certain manmade chemicals. You have likely heard that there is a "hole" in the ozone layer. Scientists believe that ozone is being destroyed as a result of pollution, specifically the use of chlorofluorocarbons (['klorə,fluərəkɑrbən]氯氟化碳), (CFCs), which are manmade chemicals used for purposes such as refrigeration. When they floated up into the stratosphere, CFCs reacted with ultraviolet radiation to create chlorine. When chlorine reacted with ozone, the chemical damaged the layer. In 1987, the leading industrial countries agreed to stop using these chemicals, but their effects may continue to be felt for a number of years to come. CFCs linger in the troposphere for years before reaching the stratosphere and the ozone layer.
    The "hole" in the ozone is most severe in the polar regions of the world. In fact, in 2006, scientists reported that the hole over Antarctica was the largest it's ever been--an average of 10.6 million square miles. That's larger than the surface area of North America!

    But there is good news! Scientists project that within the next few decades, ozone depletion from CFCs will peal and then gradually dissipate. If CFCs had not been banned in the 1980s, the situation would be a lot worse. In fact, scientists predict that by the year 2070, the big ozone holes will be a thing of the past.

    1. Why is the sun’s radiation harmful?
    ________________________________
    2. What is the main purpose served by the ozone?
    ________________________________
    3. What important thing happened in 1987?
    ________________________________
    4. Why is ozone depletion (臭氧损耗) still an issue today?
    ________________________________
    5. Which part of the earth is mostly affected?
     ________________________________

    Key:

    1.It can cause cancer, weaken our immune systems, etc.
    2.Protect us from the sun
    3.The leading industrial countries agreed to stop using these chemicals.
    4.Because their effects may continue to be felt in the future.  
    5.The polar regions.


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