help for OG-153

albert · 发表于 2003-7-13 00:13:00

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?
(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.

answer: C But I think that A is OK as well...

thanks.

tocean0222 · 发表于 2003-7-13 01:33:00

It is possible that the price of oil remains unchanged while its cost is decreasing.
So the choice A cannot be the answer.

[此贴子已经被作者于2003-7-13 1:33:59编辑过]

siebel · 发表于 2003-7-13 03:22:00

threshold的定义是：sun plants v. oil plants之间的某种比例关系。

oil fallen和oil plants fallen不是一回事儿。

C说的是oil plants，而a说的是oil。

albert · 发表于 2003-7-13 09:24:00

以下是引用tocean0222在2003-7-13 1:33:00的发言：
It is possible that the price of oil remains unchanged while its cost is decreasing.
So the choice A cannot be the answer.

[此贴子已经被作者于2003-7-13 1:33:59编辑过]

但是OG上面的解释好象并不是因为PRICE和COST的区别。。请看：
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, so choices A and E are incorrect.

能否解释解释？

albert · 发表于 2003-7-13 09:28:00

以下是引用siebel在2003-7-13 3:22:00的发言：
threshold的定义是：sun plants v. oil plants之间的某种比例关系。

oil fallen和oil plants fallen不是一回事儿。

C说的是oil plants，而a说的是oil。

但是threshold是涉及到OIL PRICE的。。THRESHOLD=OIL PRICE需要提高多少，SUN PLANTS才能和OIL PLANTS COST上可比。。

mike1999 · 发表于 2003-7-13 10:09:00

我的理解:
原文的意思是:1.科技进步和成本的降低使太阳能比过去在经济上更可行了.
2.THRESHHOLD没有变.注意力threshhold在原文的意思:假设一单位太阳能要耗费的资源相当于10$,而现在火电产生一单位的能量要耗费的资源相当于5$,10-5=5$就是这个Threshhold.这题其实可以理解为削弱题,就是削弱太阳能可行性.
C说电站的效率高了,那么有可能单位能量要耗费的资源只有3$了,(假设).那么这个threshhold就变成10-3=7 了.所以这题其实是从反面来论证太阳能经济上的不可行性.

siebel · 发表于 2003-7-13 10:47:00

以下是引用albert在2003-7-13 9:28:00的发言：
但是threshold是涉及到OIL PRICE的。。THRESHOLD=OIL PRICE需要提高多少，SUN PLANTS才能和OIL PLANTS COST上可比。。

欧觉得，这题的问题，在于对threshold的定义的理解。在欧看来，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。表明：

threshold=f(solar plants, oil plants) ---- (1)

而oil plants可能=f(oil price, other aspects) ----(2)

原题说oil price还没有涨到影响函数1的程度，并不表示oil price可以对threshold有作用。实际上，跟没说一样。

在我看来，oil price，是典型的无关选项。

albert · 发表于 2003-7-13 11:15:00

以下是引用mike1999在2003-7-13 10:52:00的发言：
A的意思刚好和答案相反.大家好好理解一下.

头痛。。我看不出如何相反了。。MIKE，请解释一下。

albert · 发表于 2003-7-13 11:24:00

以下是引用siebel在2003-7-13 10:47:00的发言：

欧觉得，这题的问题，在于对threshold的定义的理解。在欧看来，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。表明：

threshold=f(solar plants, oil plants) ---- (1)

而oil plants可能=f(oil price, other aspects) ----(2)

原题说oil price还没有涨到影响函数1的程度，并不表示oil price可以对threshold有作用。实际上，跟没说一样。

在我看来，oil price，是典型的无关选项。

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。

从这句话看来，OIL的价格对THRESHOLD是起作用的。。假设为了两个厂可比，the price per barrel to which oil would have to rise 是5￥，那么根据定义THRESHOLD就是5￥。但是在其他因数不变的情况下，如果油价跌了1元。。OIL PLANT的成本一定下跌。。SUN PLANT和OIL PLANT的成本的差距（可以理解为THRESHOLD）应该会相应的。。

所以OIL PRICE对于THRSHOLD是非常重要的。。。

siebel · 发表于 2003-7-13 11:31:00

在其他因数不变的情况下

窃以为，此假设缺乏根据。正是因为此假设缺乏根据，才导致oil price无关。

本贴相关题目 GMATPrep-2008E1-CR-82 (TUMZ)

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