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希望牛人给出解释，非常感谢！ 153. Technological improvements and reduced equipment costs have made converting solar energy directly into electricity far more
cost-efficient in the last decade. However, the threshold of economic viability for solar power (that is, the price per barrel to which oil would have to rise in order for new solar power plants to be more economical than new oil-fired power plants) is unchanged at thirty-five dollars. Which of the following, if true, does most to help explain why the increased cost-efficiency of solar power has not decreased its threshold of economic viability? (A) The cost of oil has fallen dramatically. (B) The reduction in the cost of solar-power equipment has occurred despite increased raw material costs for that equipment. (C) Technological changes have increased the efficiency of oil-fired power plants. (D) Most electricity is generated by coal-fired or nuclear, rather than oil-fired, power plants. (E) When the price of oil increases, reserves of oil not previously worth exploiting become 请问A为什么不可以，答案的解释看不明白
Since the passage of the state’s Clean Air Act ten years ago, the level of industrial pollutants in the air has fallen by an average of 18 percent. This suggests that the restrictions on industry embodied in the act have worked effectively. However, during the same period the state has also suffered through a period of economic decline. The number of businesses in the state has fallen by 10 percent, and the number of workers employed has fallen by 12 percent. It is probable that the business decline, rather than the regulations in the act, is responsible for at least half of the decline in the pollution. 13. Which of the following, if true, would most seriously weaken the conclusion drawn in the passage above? (A) During the last ten years, economic conditions in the nation as a whole have been worse than those within the state. (B) Amendments to the Clean Air Act that were enacted six years ago have substantially strengthened its restrictions on industrial air pollution. (C)Of the businesses that ceased operating in the state during the last ten years, only 5 percent were engaged in air-polluting industries. (D) Several large corporations left the state during the last ten years partly in order to avoid compliance with the Clean Air Act. （C） (E) Due to its small budget, the state office charged with enforcement of the Clean Air Act has prosecuted only two violators of the law since its passage. 请问为什么C可以，5%的公司完全可以造成很大的污染 D说明还是由法规造成的
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发表于 2009-3-5 12:42:00
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