There are some really great questions here! Since this question is so very sticky, let's revisit dan's explanation above and dig a little deeper.
This is a rather complex core structure, which is not terribly uncommon for Determine the Function questions.
Quasi-Opposing Point: People complain about electronic media killing literary skills.
Premise: But people complained about literacy killing oral culture skills.
Conclusion: Electronic media results are likely a change in the mind, not devolution of the mind.
The statement we're after is clearly the premise here - but it serves as evidence for what exactly? Keep a close eye on the author's final conclusion. His point is that our brains are just going to change, rather than shrivel up and die. Who is he arguing with? People who think our brains are going to shrivel up and die.
Who thinks that? Probably the same people who are complaining about electronic media. Why do they think our brains are going to shrivel up and die? Because they say electronic media is killing literary skills.
So, we could think of those people having a core of their very own. It would look something like this:
Complainers' Premise: Electronic media is killing literary skills.
Complainers' Conclusion: Therefore, our brains are going to devolve!
The author pats them on the head and tells them not to worry. Something similar to what they are worried about happened long long ago. (It's implied that our brains did not shrivel up and die back then). So, he concludes, they probably aren't going to shrivel up and die now.
Note that the author never, ever disputes that electronic media might be killing our literary skills. His conclusion is entirely about whether our the human mind will devolve as a result. To support the claim that it won't, he points to a situation where a new skill (literacy) arguably killed off an old skill (oral culture skills), and yet our minds did not devolve. This is expressed in (C).
The Vile Temptress (D)
(D) is incredibly tempting. We know we have an opposing point, we know the author is using this statement as evidence to support his own point somehow - so this looks like water in the desert to us if we aren't careful.
But make sure your language radar is set at high scan! This answer says the statement is evidence that the claim is unwarranted. The author never actually says anything is unwarranted. mrudula_2005 is correct that the author's conclusion is soft and weak, with a 'probably', instead of a bold 'that's unwarranted!' claim.
However, that's not the only problem. The author's claim is that the unspoken opposing conclusion is probably incorrect. The author never says a thing about the idea that electronic media is killing our literary skills. That concept is really the premise of the opposing camp, and the author just disagrees with their conclusion (that our minds will devolve).
Also Not the Function
(A) The statement is evidence, for sure, but not for the claim that electronic media is killing literary skills. That's the opposition's complaint!
(B) "the means by which people communicate" is a language shift; the argument is not at all about the concept of "inseparability", nor is the conclusion a general hypothesis (rather it is a qualified prediction).
(E) This statement is not dismissed; it is also not evidence the opposition would draw on to support their argument (that our minds will devolve).
This is a very tough question! Please let me know if you have any additional concerns on this, or anything to add to the discussion!
#officialexplanation