作者：英吉
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
原文意思：不想emergency calls要求operator怎么操作，cellular calls要求operator怎么操作
题目分析：不象emergency call，后面必须说cellular call才能和前面对应，A这点符合，留着 B也留着。CDE后面说的东西无法和前面的unlike emergency calls对应，干掉。A前面还用了个they，B就一气呵成说下来了，加了they只会让我联想多一些，B更好！
