7. Traverton’s city council wants to minimize the city’s average yearly expenditures on its traffi c signal lights and so is considering replacing the incandescent bulbs currently in use with arrays of light-emitting diodes (LEDs) as the incandescent bulbs burn out. Compared to incandescent bulbs, LED arrays consume significantly less energy and cost no more to purchase. Moreover, the costs associated with the conversion of existing fixtures so as to accept LED arrays would be minimal.
Which of the following would it be most useful to know in determining whether switching to LED arrays would be likely to help minimize Traverton’s yearly maintenance costs?
(A) Whether the expected service life of LED arrays is at least as long as that of the currently used
incandescent bulbs
(B) Whether any cities have switched from incandescent lights in their traffi c signals to
lighting elements other than LED arrays
(C) Whether the company from which Traverton currently buys incandescent bulbs for traffi c
signals also sells LED arrays
(D) Whether Traverton’s city council plans to increase the number of traffi c signal lights in
Traverton
(E) Whether the crews that currently replace incandescent bulbs in Traverton’s traffi c signals
know how to convert the existing fi xtures so as to accept LED arrays
我想问这道题为啥不能选E。
我的思路：首先是一道评价题。然后评价的是结论，老师说的肯定和原因特别相关。那E不就是说得和原文的原因吗？（原文原因：Moreover, the costs associated with the conversion of existing fixtures so as to accept LED arrays would be minimal）不就是说转换成本吗？作者: victoria820 时间: 2010-11-26 19:16
(E) Whether the crews that currently replace incandescent bulbs in Traverton’s traffi c signals
know how to convert the existing fi xtures so as to accept LED arrays
你没看明白这句话
E的意思是：是否工作人员知道怎么换
这题的结论是：要换LED 为了minimize the city’s average yearly expenditures
E和这个结论一点关系都没有
A 选项谈到使用寿命，如果LED寿命短，要经常的换，成本就会很高了，所以这个是评价结论的关键作者: nymphl 时间: 2010-11-27 19:11
花费= 电费+灯泡成本
而灯泡成本= 灯泡单价 x 更换频率， 更换频率 与 使用寿命成反比
A 考虑的就是更换频率
E 是一个明显的无关选项作者: angelsgx 时间: 2010-11-28 06:58
明白了，谢谢大家
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