C is wrong because it makes it seem the three networks broadcasting the same statement from the political candidate is a precursor for superficiality when the example is really trying to elucidate the point that the similar broadcasting is an example of superficiality. Hence the "as when" phrase of option E. I hope this makes sense.

83. 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
// such as used to give examples. Thus, the above construction is unidiomatic.
Also each should be followed by broadcasts.. sub-verb agreement..

(B) superficial, as can sometimes occur if all of the three major networks
// if construction not desired

(C) superficial if the three major networks all
// same reason as b

(D) superficial whenever each of the three major networks
// each.. should be followed by broadcasts..

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

83. 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
Incorrect : "such" is redundant.

(B) superficial, as can sometimes occur if all of the three major networks
Incorrect : Tense used "as can" in improper.

(C) superficial if the three major networks all
Incorrect : "if" should be used in case sentence is conditional

(D) superficial whenever each of the three major networks
Incorrect: "Whenever" changes the meaning of the sentence.

(E) superficial, as when the three major networks each
grammatically correct and compact

what is the function of "as when" in E?

i can see it is very easy to use underline function here...
why are people not using it....
it is making question more complicated while reading