In recent years, networks of fiber-optic cable have been replacing electrical wire for transmitting...

题目信息

In recent years, networks of fiber-optic cable have been replacing electrical wire for transmitting telecommunications signals. Signals running through fiber-optic cables deteriorate, and so the signals must be run through a piece of equipment called a regenerator before being transmitted farther. Light-Line is the leading manufacturer of signal regenerators. Therefore, Light-Line is one of the companies that will most benefit if new long-distance fiber-optic telecommunications networks are constructed.

Which of the following, if true, casts the most doubt on the prediction about Light-Line's prospects?

A:Telecommunications signals sent along electrical wires can travel much farther than signals transmitted through fiber-optic before needing to be regenerated.

B:Expanding its production of regenerators will require Light-Line to spend proportionately more on labor and materials.

C:The volume of signals that a fiber-optic cable can carry is several thousand times greater than the volume that can be carried by an electrical wire of similar size.

D:There are technologies that enable telecommunications signals to be transmitted without either wire or fiber-optic cable.

E:Several manufacturers are developing regenerator technologies that will allow signals to be transmitted many times farther than at present before requiring regeneration.

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正确答案： E:Several manufacturers are developing regenerator technologies that will allow signals to be transmitted many times farther than at present before requiring regeneration.

光电传输有个距离限制，超过一定距离信号就会衰减，所以要用regenerator把完整的信号向下继续传送。

A中所说的：electrical wires比没有generate的fiber-optic要远，这个在题目逻辑链中没有关系，况且已经开始用fiber替代wires了必然是fiber要好。无关

B中只是简单的陈述了扩大generator的生产量，不能得出L-L公司所得到的benefit就会少。

C中比较了fiber-optic比electrical wires的优势，与逻辑链无关，因为逻辑链所指是生产generator与L-L公司利益的关系

D和E最大的区别是题目限定了条件范围，是在这个....的建设之下。D直接说不建设了。

E正确。别人做得regenerator可以把信号传的更远，同等距离需要regenerator的数量减少。会削弱对LL的需求

笔记