本贴相关题目 GMATPrep-2008E1-CR-82 (TUMZ)

00:00:00

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?

AThe cost of oil has fallen dramatically.
BThe reduction in the cost of solar-power equipment has occurred despite increased raw material costs for that equipment.
CTechnological changes have increased the efficiency of oil-fired power plants.
DMost electricity is generated by coal-fired or nuclear, rather than oil-fired, power plants.
EWhen the price of oil increases, reserves of oil not previously worth exploiting become economically viable.

正确答案: C

新prep2-82

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alanuonuo

楼主

发表于 2010-7-29 00:49:35 | 显示全部楼层

过去: 太阳能发电成本 - 石油发电成本 = 35美圆

现在: 太阳能发电成本下降了, 但仍然太阳能发电成本 - 石油发电成本 = 35美圆

解释: 石油发电成本也下降了.

而threshold就是两种发电厂的成本之差

A：油价只是衡量threshold一个因素，但是不是确定threshold关键的因素，因为还有别的因素例如人力，原料或者别的什么

而题目中提到说，太阳能转化的效率提高（即成本下降），而threshold不变，那么从公式(3)中就很容易得到：是因为石油转化成电能的成本也降低了（即石油发电效率提高）。

所以选C。

-- by 会员 xfi883 (2009/7/4 23:17:00)

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