请教NN们PREP新破解里的一题～

82.   (33511-!-item-!-188;#058&007598)

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.

答案是C，能理解。

但是找不出很好的理由排除A，希望NN们解答～

threshould= 石油能成本 与 太阳能成本 的差额

如果threshould未变，太阳能成本降低，那么石油能成本必须降低，推出石油能效率增加

文中说效率增加的原因为technological improvement and reduced equipment costs，

A选项中说石油的成本降低，文中没有说oil-fired power plants与石油的关系，是楼主自己推测的哦～～