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【单选题】
When scientists first warned in the 1970s that CFCs could attack ozone, the U.S. responded by banning their use in spray cans. But the rest of the world continued to use CFC -based aerosol cans, and overall CFC production kept growing. The threat became far clearer in 1985, when researchers reported a 'hole' in the ozone layer over Antarctic. Although the size of the bole varies with the seasons and weather patterns, at times Antarctic ozone has been depleted by as much as 50% in some spots. As a result of this disturbing de- velopment,24 nations, including the U. S. and the Soviet Union, met in Montreal two summers ago and a- greed to cut back on CFCs. The so - called Montreal Protocal is designed to achieve a 35% net reduction in worldwide CFC production by 1999. That’s not good enough, however, the same stability that makes CFC so safe in industrial use makes them extremely longlives, some of the CFCs released today will still be in the atmosphere a century from now. Moreover, each atom of chlorine liberated form. a CFC can break up as many as 100,000 molecules of ozone. For this reason, governments should ensure the careful handling and recycling of the CFC now in use. When plastic-foam burger holders are broken, the CFCs trapped inside escape. Discarded refrigerators re- lease CFCs as well, and, a significant part of the U.S. contribution to CFC emissions comes from draining automobile air conditioners. Such release of CFCs could be prevented if consumers and businesses were offered cash incentives to return brokendown air conditioners and refrigerators to auto and appliance dealers. Then the units could be sent back to the manufacturers so that the CFCs could be reused. While recycling will help, the only sure way to save the ozone is a complete ban on CFC manufacture, which should be phased out over the next five years. Fortunately, as the Montreal Protocal demonstrates, banning CFCs will be far simpler than reducing other dangerous gases. But a ban could admittedly be economically disruptive to the entire world: the annual market for CFCs is some $ 2.2 billion. The Soviet Union, which is a heavy user of CFCs, will have a particularly tough time phasing out the chemicals. 'I agree with the ban in principle, 'said Vladimir Sakharov, a member of the Soviet State Committee for Enviromental Protection, 'but in practice it will be extremely difficult. Our economy is not flexible as others.' To make the transition easier, chemical companies are working hard to find practical substitutes for CF- Cs. The most promising approach so far is to use CFC family members that are chemically altered to make them less dangerous to the environment. The chlorine - free substitutes is the high cost of making them. It may be that until better manufacturing techniques are developed, consumers will have to pay more for affected products. The prospect is not a pleasant one, it is a small price to pay for curbing tile green house effect and saving the life -preserving ozone layer. Why should governments ensure tire careful handling and recycling of the CFCs now in use?
A.
Because the CFCs directly damage the people's health.
B.
Because the CFCs are poisonous chemicals.
C.
Because the production of the CFCs costs a lot.
D.
Because the CFCs can attack ozone by liberating atoms of chlorine.
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参考答案:
举一反三
【单选题】可用()来检测冷却液冰点
A.
观察法
B.
沸腾实验法
C.
冰点测试仪
D.
以上都对
【单选题】下列哪一种情形,人民能获得最大的“自由”?
A.
司法权与立法权和行政权分离
B.
司法权与立法权合并
C.
司法权与行政权合并
D.
三权合并
【单选题】可用( )来检测冷却液冰点。
A.
观察法
B.
冰点检测仪
C.
沸腾实验法
D.
以上都对
【单选题】有关完全培养基中胎牛血清的说法正确的是
A.
血清和胰蛋白酶的作用相反
B.
胎牛血清是血清中的一种,在细胞体外培养基中可加也可不加
C.
胎牛血清也可以用合成的血清替代
D.
提供对维持细胞指数生长的激素,基本培养基中没有或量少的营养物以及低分子营养物质;某些情况下结合蛋白质能与有毒金属结合,起到解毒作用;细胞贴壁、铺展所需因子的来源
【简答题】Schools are bad businesses, whether public or private, not usually because of bad management but because of the nature of the business.
【简答题】A.Because he had run out of gas. B.Because his tires were stabbed. C.Because he bad heard a noise. D.Because he was attracted by Mrs. f Jones.
【简答题】A.Because of the bad weather. B.Because of his young age. C.Because he lost his way while crossing the ocean. D.Because he had no partner to help him.
【简答题】《灵枢·营卫生会》说:“上焦如雾,中焦(),下焦如()”。
【单选题】Why will the plane take off late?
A.
Because of bad weather
B.
Because the working conditions for Paraguay Airlines staff are poor
C.
Because the captain is four hours late for work
D.
Because there is a strike
【单选题】有关完全培养基中胎牛血清的说法正确的是()
A.
提供对维持细胞指数生长的激素,基本培养基中没有或量少的营养物以及低分子营养物质;某些情况下结合蛋白质能与有毒金属结合,起到解毒作用;细胞贴壁、铺展所需因子的来源
B.
胎牛血清也可以用合成的血清替代
C.
胎牛血清是血清中的一种,在细胞体外培养基中可加也可不加
D.
血清和胰蛋白酶的作用相反
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