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标题: PREP08-82看了所有讨论帖，知道为什么选C 但是A错在哪里呢？ [打印本页]

作者: barbaradu 时间: 2012-3-3 12:51
标题: PREP08-82看了所有讨论帖，知道为什么选C 但是A错在哪里呢？
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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 economically viable.
求赐教！！！

作者: kevingod 时间: 2012-3-3 14:53
这个关键是threshold的定义：是太阳能电厂比燃油发电厂更economical时，每桶油应该达到的价格。而不是应该增加的价格，注意文中用的是“to",不是“by"!
所以临界条件是，两个同样economic efficiency.这样看来C选项直接提到efficiency当然更好。
至于A选项，LZ可能是误解了定义，就是“to"和“by”的区别。这个threshold其实是跟当前油价没有关系的，它指的是经济效率相等时油应该达到的价格，与经济效率直接挂钩，是一个理论值。而无论油价怎么变，只要经济效率不改变，这个理论值是不会变的。

作者: barbaradu 时间: 2012-3-3 17:55

这个关键是threshold的定义：是太阳能电厂比燃油发电厂更economical时，每桶油应该达到的价格。而不是应该增加的价格，注意文中用的是“to",不是“by"!
所以临界条件是，两个同样economic efficiency.这样看来C选项直接提到efficiency当然更好。
至于A选项，LZ可能是误解了定义，就是“to"和“by”的区别。这个threshold其实是跟当前油价没有关系的，它指的是经济效率相等时油应该达到的价格，与经济效率直接挂钩，是一个理论值。而无论油价怎么变，只要经济效率不改变，这个理论值是不会变的。

-- by 会员 kevingod (2012/3/3 14:53:15)

灰常感谢！！！解释很清楚，又读了几遍题意，明白啦！

作者: teddybearj4 时间: 2012-4-10 20:35
这道题太抽象了！

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