OG-153求解

不理解the threshold of economic viability之意 (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)

(A)(E)为何不对，看了OG解释仍不明白

附上OG解释Actual oil prices control how far, given the viability threshold, solar power is from economic viability but do not figure in the determination of the threshold.  

先谢过

Technological improvements and reduced equipment cost have made converting solar energy directly into electricity far more cost-efficient in the last decade. However, the threshold of economic viability is (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)unchanged at thirty-five dollars.  

(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.

Ans: C      

太阳能发电的成本：生产的费用+阳光（免费）

石油发电的成本：生产费用+石油（不免费）

在两种生产方式的现有效率（也就是生产费用）一定的时候，使“solar发电的生产费用=oil发电的生产费用 + 购买oil成本“的购买石油成本就是threshold。这个threshold越低，现行的油价就越可能高于threshold，石油发电的总成本就高于solar发电。solar电厂的人是盼者这个threshold下降的，方法只有一个，solar电厂提高自身效率，降低生产成本。

现在solar发电的生产费用降低了，也就是等式左边变小了，为什么threshold还将不下来呢？只有一种可能：oil发电的生产费用也降低了。

不好意思，讲的不清楚，希望mm能领会。

这道题的关键是理解这个threshold的定义，理解了，不选A，E就清楚了。

按照提干的解释就是：solar power plants在保持其相对于oil fired power plants的经济优势的情况下，oil可以提高的价格。举个例子，如果SPP的价格是10，而OFPP的价格是2，那么如果要保持SPP的价格优势，oil只能上升8。说白了就是SPP和OFPP的差价。

那么按题干所说，SPP的成本降低了，但是它和OFPP的差价没有变，问原因。那就只有OFPP的成本也下降了。

A说的是oil没有说OFPP，而E依旧在将oil的价格，没有说到OFPP，所以错，因为我们要求正的是OFPP。OG的解释正是这个意思。

我认为C,A都对.

threshold 是OIL 和SOLAR 的差距(OIL 需要上涨的价格从而使SOLAR 经济上可行), SO A IS RIGHT.

试想你是一个选择OIL , SOLAR 的MANAGER, 现在OIL's price falls dramatically, 你会选SOLAR吗?