题都没看懂啊。。。。。求讲解，为什么不选B呢？

honeybee316

Technologicalimprovements and reduced equipment costs have made converting solar energydirectly into electricity 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.
Whichof the following, if true, does most to help explain why the increasedcost-efficiency of solar power has not decreased its threshold of economicviability?
A.The cost of oil has fallen dramatically.
B.The reduction in the cost of solar-power equipment has occurred despiteincreased 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 worthexploiting become economically viable.

StephenHawking

我觉得A跟threshold没什么联系，即使cost降了，跟发电效率什么的也联系不上啊

hanshipeng

我的第一反应是A。。。C的确是一个正确的选择，但是有什么办法能排除A呢？

zhangfan90

B选项没有说出Solar power plant 的economical viability 保持不变

的原因。你可以换个角度想：从oil power plant的方面考虑一下。 括号里

面（。。。l to which oil would have to risein。。）会有一些暗示。