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  3. Scientists in the United States have reported some good news about the ozone in the atmosphere. Recent findings suggest that the

Scientists in the United States have reported some good news about the ozone in the atmosphere. Recent findings suggest that the

admin2012-09-19  73
问题     Scientists in the United States have reported some good news about the ozone in the atmosphere. Recent findings suggest that the destruction of ozone by pollution is slowing. Ozone is a form of oxygen. Its presence above earth protects us from radiation from the sun.
    In one study, researchers examined information gathered by space agency satellites and by equipment on earth. The findings are, in the words of Michael Newchurch of the University of Alabama: "This is the beginning of a recovery of the ozone layer." Mr. Newchurch led the study. He says the atmosphere was losing about 8 percent of the ozone layer per 10-yeas period since the late 1970s. In the last 5 years, though, that rate of loss has dropped by half. He says the atmosphere should start to gain ozone before long. He says a full recovery, however, is about 50 years away, as long as the Montreal Protocol remains in place.
    That is an international treaty from 1987 to restore the ozone layer. The treaty restricts the use of a number of chemicals that destroy ozone, like chlorofluorocarbons(氯氟碳化合物), or CFC.
    Wide use of CFC began in the 1930s, They became popular coolants in devices such as refrigerators and air conditioners. CFC remains in the atmosphere fox years.
    Mr. Newchurch says the study provides evidence that the Montreal Protocol is working by reducing CFC pollution, But the study found the ozone improvement only in the upper stratosphere(平流层). The scientists have not yet seen evidence of similar changes in the lower stratosphere. That holds most of the protective ozone.
    The Montreal Protocol also restricts the use of methyl bromide(甲基溴), a chemical to kill insects. Farmers and shippers are the main users.  Natural sources of methyl bromide include oceans and some plants. Scientists say the bromine gas it produces is 50 times more destructive to ozone than chlorine(氯气)gas from CFC.
    Methyl bromide has never been used as widely as CFC. But a separate study found a decrease in bromine gas levels in the atmosphere. Researchers at the National Oceanic and Atmospheric Administration did the study. They reported a 13 percent drop since 1998. The report is based on 8 years of measurements taken at 10 stations around the world.
The Montreal Protocol, an international treaty, is aimed at ______.
选项 A、restricting uses of CFC
B、restricting uses of methyl bromide
C、banning uses of CFC
D、restoring the ozone in the atmosphere
答案D
解析 根据题干内容，在文中查找the Montreal Protocol的目标，从文中第四段的第一句话可知，蒙特利尔议定书签订于1987年，目的是为了恢复臭氧层，故选D)。本题解题的关键就是切忌把手段当成目的，削减使用CFC、methyl bromide等都是蒙特利尔议定书为了恢复臭氧层而采取的措施手段，所以A)、 B)都予以排除；而C)，禁止使用CFC，与文中意思不符。
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