GWD21逻辑一道求助！！！

KingsDi

In recent years, networks of fiber-optic cable have been replacingelectrical wire for transmitting telecommunications signals. Signals runningthrough fiber-optic cables deteriorate, and so the signals must be run througha 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-distancefiber-optic telecommunications networks are constructed.

Which of the following, if true, casts the most doubt on the predictionabout light-line’s prospects?

A.     Telecommunications signals sent along electrical wires cantravel much farther than signals transmitted through fiber-optic before needingto be regenerated.

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

C.     The volume of signals that a fiber-optic cable can carry isseveral thousand times greater than the volume that can be carried by anelectrical wire of similar size.

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

E.      Several manufacturers are developing regeneratortechnologies that will allow signals to be transmitted many times farther thanat present before requiring regeneration.

对于D，E有点模糊...  正确是E， 求NN解释！   跪谢！！！