prep-63同位语从句并列的that省略问题

Unlike emergency calls that travel through regular telephone lines, where they thus automatically inform the operator of the location and phone number of the caller, cellular calls require emergency operators to determine the location of the caller.

(A) lines, where they thus automatically inform the operator of the location and phone number of the caller, cellular calls require emergency operators to determine the location of the caller

(B) lines and
            thus automatically inform
            the operator of the location and phone number of the caller, cellular calls require emergency operators to determine the location of the caller

(C) lines, thus automatically informing the operator of the location and phone number of the caller, the location of the caller on a cellular phone has to be determined by the operator

(D) lines, and thus automatically inform the operator of the location and phone number of the caller, emergency operators have to determine the location of the cellular phone caller

(E) lines, thus automatically informing the operator of the location and phone number of the caller, emergency operators receiving a cellular call have to determine the location of the caller

正确答案是Ｂ想请问一下　这里 travel 与inform平行却省略了that　是由于这个是同位语从句吗？？以前见过一次有人讨论　但不是十分确定～十分谢谢

ＬＳ说的好象有道理．．．我糊涂了．．．～～～

那种that and that 应该是什么样的啊？？