新prep 第二部分 82

jasonlove

82.   
Technological improvements andreduced equipment costs have made converting solar energy directly intoelectricity far more cost-efficient in the last decade.  However, the threshold of economic viabilityfor solar power (that is, the price per barrel to which oil would have to risein order for new solar power plants to be more economical than new oil-firedpower 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 hasnot decreased its threshold of economic viability?
A. The cost of oil has fallendramatically.
B. The reduction in the cost ofsolar-power equipment has occurred despite increased raw material costs forthat equipment.
C. Technological changes haveincreased the efficiency of oil-fired power plants.
D. Most electricity is generated bycoal-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.


求救啊，对这个argument，不懂point在哪里，特别是括号里的东西，是什么意思，和问题有何联系？thx~

sealg

选C，这是solar power palnts 和oil power plants的比较，第一句说solar power plants效率高，但是结论说门槛没有降低，需要的条件是oil power plants 也效率提高了，选C

jasonlove

谢谢，我看了解释也是说门槛什么的。在这里，门槛是什么意思啊

sevenmileser

threshold就当做津贴税，也就是为了使得同等效力下使用太阳能的工厂比石油工厂有吸引力，那么必须在每桶石油成本价基础上加35美元才能保障。
那么既然使用太阳能的工厂的成本降低了（因技术提高），为什么石油津贴税还是很高，只有一个可能性就是同时使用石油的工厂的成本也降低了（同样因技术提高）。c
而a不选是因为，即使石油价格降低，那么油价下降的比例必须和太阳能工厂降低的成本有同幅度的效应，dramatically是个很模糊的词汇，20%和80%都可以修饰，所以A有关系，但是不准确。

Steven0124

哦，谢谢了！！