这道题肯定不是C

yya

新prep上的一题，答案是C ,可是本人认为A跟好，请教各位大牛

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.

salasbond

我认为答案就是C。

题干：Tech improvement of solar E increased cost-efficiency. But the threshold of economic viability of solar power is unchanged at 35 bucks.

问题：哪个能说明为什么 incresed cost-efficiency of solar power didn't decrease the threshold of economic viablity of solar power.

分析：先不看选项，分析原因有以下可能
1. solar E原料贵了，所以compensate了，Tech带来的技术提高
2. 其他形式Energy的Tech也提高了，所以solar E的threshold，还是那样。

看看选项，选C

A错在，混淆了概念cost of oil和efficiency of oil-fired power。油价可以低不过不能保证efficiency高，因为可能管道维修贵了，石油工人工会工资问题......，只是举2个例子。意思说cost of oil和efficiency of oil-fired power的联系是主观的建立的，而不是题目已经给的。
B错在，支持反了
D错在，题干中没有涉及的无关选项
E错在，同B，同A

ki87uj

LS的分析太牛了。。。

九段泡面高手

其实就是solar技术进步了，我oil技术也进步了而已??不过A说实话一瞬间我还真没看出问题，不过感觉C更紧贴题意罢了，看了2楼对于A的解释，我不得不说我被2楼睡服了

jiaoguitar

我来稍微补充一下2楼的解释。题目说的是10年前与10年后每桶石油价格都需要增加到35刀(to which the oil rise)，Solar power plants 才具备对 oil-fired power plants的竞争力。

也就是说比较对象是power plants之间展开的，而不是Oil和Solar本身。A选项提到Oil而不是提到power plants，是典型的Shell Game选项。GMAC很喜欢出这样的迷惑选项。

B是无关选项；C提到了解决这个矛盾的一种可能，便是Oil power plants效能提高，另一种可能是Oil power plants的价格下降，也就是改写A为正确选项的办法；D和E都是无关选项。

但愿我的解释更清楚一些。

hi1177

我认为2楼说的很好很精辟。4楼说的也很好很精辟。我表示很佩服。因为这题我也选了A = =

angelica812

4楼的完全解惑！！！我也选了a

jackhouse

再想想啊

guaiss

salasbond 发表于 2010-4-8 23:41
我认为答案就是C。题干：Tech improvement of solar E increased cost-efficiency. But the threshold of e ...

虽然我也觉得C对
但如果照这个说法的的话 C选项也是有问题的
混淆了概念efficiency 和 cost-efficiency
efficiency提高不一定会使cost-efficiency提高
如果efficiency提高了 但是油价涨了好几十倍 成本还是大幅提高了
也就是说A和C都需要在一定的前提下才可以support结论

Vivian1091

salasbond 发表于 2010-4-8 23:41
我认为答案就是C。题干：Tech improvement of solar E increased cost-efficiency. But the threshold of e ...

二楼讲的很清楚了。看曼哈顿论坛上tim举了例子说明这个道理，不懂的同学看下
This seems to be a popular (and quite misunderstood) problem, so I'm going to take one more stab at explaining this one:

The question is essentially asking why the threshold of economic viability has remained unchanged. In other words, why would the price of oil still have to hit $35 in order for solar powered plants to be a good idea?

A lot of people are asking why A isn't the correct answer. The best answer I can give is that the price of oil has nothing to do with how much the price *would* have to be in order for solar power to be viable. Consider this: if I have $20000 available to buy a car, the "threshold of economic viability" for me to buy a car is $20000. What if the price of a car is $30000? Doesn't matter, I still can't buy a car unless it's less than $20000. What if the price suddenly drops to $10000? Doesn't matter; even though I can now buy the car (yay), this price drop didn't change the fact that I could only buy a car if it were less than $20000. What would change my threshold of viability? NOTHING about the price of the car can change my threshold; my own personal threshold of $20000 would only be changed by something that had to do with my own purchasing power - I make more money, the bank gives me a better interest rate, etc.

In a similar sense, the reason the threshold of viability has not changed in this problem has nothing to do with the price of oil, but instead has to do with how cost-effective solar power is relative to oil power. C does this by providing a scenario in which efficiency increases in solar power are balanced by efficiency increases in oil power.


_________________
Tim Sanders
Manhattan GMAT Instructor

http://www.manhattangmat.com/forums/cr-technological-improvements-and-reduced-equipment-costs-t7885-15.html