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，铁板钉钉。
但是，我就是想不通为什么A不可以？而且A里面还有个dramatically呢，oil的大大的降低了，所以用太阳能的经济优势无法体现啊。
哪位兄弟能告诉我，我到底哪里想错了。
谢谢！
首先the threshold of economic viability for solar power，意思是说solar power是否可行视乎一个门槛，这个门槛就是石油的价格，只有当石油的价格达到或高于35美金一桶的时候，new solar power plants才比new oil-fired power plants更economical。
科技的进步已经有效的降低了solar power的成本，但35这个门槛却一直没有降低。需要你解释其中的原因。答案A看似和石油价格有关，其实和问题无关。石油价格大幅降低，解释不了为什么solar power的成本低了，但35这个门槛却不变。
只有答案C合理解释。那是因为科技进步同样增加了new oil-fired power plants的效率，从而降低了成本。当比较双方同时降低成本或增加效率的时候，35保持不变。
篮字部分就是楼主疑惑的地方贝
| 欢迎光临 ChaseDream (https://forum.chasedream.com/) | Powered by Discuz! X3.3 |