一道不会的题，主谓一致方面的

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 statesmen 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 suerficial if the three major networks all

请问c为何错
D superficial whenever each of the three major networks

E superficial, as when the three major networks each