一道PP3,怎么也读不明白

Technological improverments and reduced equipment costs made

converting solar energy directly into electricity far more cose-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 ecnomical 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 eco-

nomic viability?

A  The cost of oil has fallen dramatically.

B   The reduction in the cost of solar-power equipment has occured

    despite increased raw material costs for that equipment.

C  Technolofical changes have increased the efficiency of oil-fired

 power plants.

答案C,

请问，括号里面那句，怎么翻译？谢谢了

括号里面的东西是蒙人的。题意是虽然技术进步了，但是其和火力发电的比较，还是不如火力发电。所以答案基本要么是 火力发电viabilty远远领先，太阳发电的进步没用； 要么是火力发电也进步了。 好像是一个比例， A/B =k  , A增加了，但是k依旧没达到一个值,其原因要么B太大，要么是B也增加了

哦，终于搞明白了，thanks！