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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. C (E) When the price of oil increases, reserves of oil not previously worth exploiting become economically viable.
153. If gains in cost-efficiency of solar power have not improved its economical viability relative to oil-derived power, the explanation must be that oil-derived power itself has become more cost-efficient. Choice C points to this explanation and is thus the best answer.
Actual oil prices control how far, given the viability threshold, solar power is from economic viability but do not figure in the determination of the threshold, so choices A and E are incorrect. Choice B provides background on data that give rise to the puzzle but leaves the puzzle unresolved, so it is incorrect. Because the viability threshold for solar power is defined in relation to generating electricity from oil, choice D is irrelevant to determining the threshold and thus incorrect. 请大家帮忙解释一下什么意思好吗? | 
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发表于 2008-4-8 20:16:00
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