On any Text Completion question, it is important to follow contextual clues to help eliminate answers that are not justifiable. I would argue that this skill is more important than actually having 1,500 vocabulary words memorized, since contextual understanding will also help with Reading Comprehension questions. Here, if we strip down the first independent clause of the sentence, we get, "To claim that the prevailing account is corrupted by disinformation is to enter _____ waters." The keywords are claim, corrupted, and disinformation. The first, claim, indicates that the view is not necessarily correct, while the second casts aspersions on the account, a bold maneuver, and the third is a specific charge, namely that disinformation lies at the heart of the corrupted account. Looking at the first three answer choices, you have to ask yourself, what does familiar have to do with any of the above analysis? Absolutely nothing, so toss it. Then, although uncharted waters is an idiom we use to indicate that an experience is new or untested, again, the connection to the keywords is tenuous at best. That leaves treacherous as the answer by default, but when you stop and think about it, it makes sense. A treacherous action could be accusing someone or something of corruption.
The second independent clause starts with the conjunction "for," so we know that an explanation is going to follow. For instance, take a model sentence: She ought to do well on the test, for she has been studying three hours a day. The second clause provides the reason for the statement that preceded it. In the sentence in question, we have, "Any subsequent account is similarly _____ such charges." Rather than get caught up in charges, which could just as well be some other noun, we should be focusing instead on the keyword similarly. Whatever fits into the second blank must describe a scenario that relates to what we have just read in the first main clause. Test the answer choices: "Any subsequent account is similarly related to such charges." That could be true, but the frame of the phrase, "Any subsequent account is," calls for a must-be-true instead. For all we know, a subsequent account could be completely different, adding other charges instead. Scrap the first choice. How about the second? "Any subsequent account is similarly guilty of such charges." Going back to what we established before, we do not know whether the claims have any merit, so guilty of overstates the case. That leaves the other answer, not immune to, as the last domino standing. Why does it make sense? Because the sentence is indicating that, due to the nature of the claim, any extension of that claim would also in some way tie into corruption by disinformation. Thus, any subsequent account offered is similarly not immune to such charges fits all the contextual clues, and it must be the correct response.
I hope that helps. Good luck with your studies.