gmej的大全83求助

1.        Although it claims to delve into political issues, television can be superficial such as when each of the three major networks broadcast exactly the same statement from a political candidate.

(A) superficial such as when each of the three major networks

(B) superficial, as can sometimes occur if all of the three major networks

(C) superficial if the three major networks all

(D) superficial whenever each of the three major networks（E）

(E) superficial, as when the three major networks each

本来以为each应该接单数的谓语, 但lzm的语法书说"名词+each"做主语, 谓语与前面名词一致, 这样e是没有主谓不一致的问题了, 可C也没什么问题啊? 也比E的as when更常用, 为什么不能选呢?