section 17 No.14/大全-17-14

browse

14.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. A
(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.

答案选C,但A错在哪儿呢，如果cost of oil fallen dramatically, threshold of economic viability for solar power 肯定上升，但由于cost-efficiency of solor power has increased, 所以threshold没变呀。
而且也看不出A和C谁更重要。
NN指点一下。

jandj_shanghai

呵呵，A的确很迷惑阿。
不过注意是threshold是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

关键是这个threshold其实是指多少量的solar相当于多少量的oil。

比如原来oil1块钱1barrel发35度电，35块钱1个solar发35度电。threshold是oil升到35块钱1barrel。

现在solar的efficiency提高了，35块钱1个solar发350度电。如果其他未变，则35块钱1个solar相当于10barrel的oil。那么这个threshold是oil升到3.5块钱1barrel。

C但是如果oil的efficiency也提高了，0.1barrel的oil可以发35度电。那么35块钱的1个solar发350度电，相当1barrel的oil。threshold还是35/barrel。

A不管油价上升还是下降，这个threshold都从35/barrel变到了3.5/barrel。A只是说相同的钱买到的oil随着油价下降而增多了，并不能改变threshold随着solar efficiency的提高而降低的事实。

[此贴子已经被作者于2003-11-29 13:14:25编辑过]

browse

漠漠呼呼，还是不是很清楚，厉害啊大虾。可能自已智商下降了

cranberry

题目比较的是燃油发电的成本和太阳能发电的成本,因为燃油的价格只是其发电成本的一个方面,而整个平均成本是  总成本/总产量,C说的正是这个比率的提高,所以C更好.

rt316

举例说明：


原来：


太阳能发电，每生产一度电，成本60；


油发电，每生产一度电耗机械成本10，买油花15，


于是，两者之间的成本差为35；


现在：


太阳能发电，每生产一度电，成本50；


油发电，每生产一度电耗机械成本10，买油花5，


于是，两者之间的成本差仍然为35；


得出结论：现在油发电每一度电的油少了，即效率增加。


    


    

bobobear

我觉得关键在这里：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)是指油价必须涨到多少，才能使太阳能发电有实用价值。

a中，油价下跌是无关的。只要太阳能发电效率提高了，而油发电效率不变，这个threshold就应该下降。

一起加油的夥伴

我覺得這題似乎是這樣的意思

threshold是指     the price per barrel of solar plants       分子

                           the price per barrel of oil-fired plants   分母

因為原文有說,threshold is unchanged,且太陽能的成本是下降的

所以推得 the price per barrel of oil-fired plants 的成本也是下降的

選項 A不對的原因是因為 oil成本的下降不代表the price per barrel of oil-fired plants下降

望請指正

   

[此贴子已经被作者于2005-11-17 14:32:45编辑过]

zxzhyzcy

以下是引用一起加油的夥伴在2005-11-17 14:30:00的发言：

選項 A不對的原因是因為 oil成本的下降不代表the price per barrel of oil-fired plants下降

望請指正

同意同意！！！就是cost和price的概念被偷换了吧~~个人认为~

heiniba

油价需要涨到35美元，用solar才比oil-fire划算。因此油价下降跟efficiency没有关系吧。

等NN拍。。。

pharmacystar

同意  6楼的说法

就是油的价格和效率是两回事

我们讲的是效率

所以A不对，C对