请问OG-153

大家帮我看看题目是不是有问题？
153. 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?
~~~~~~~是不是应该是increased?我用的电子版，错误狂多,sigh,很影响自信心的说

(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.
顺便帮忙翻译一下提干好吗？谢谢了！