Official Explanation

A,F,G

The key to this question is the contradiction between the group's voting behavior before the election and in the election itself. The single word before the comma in blank (i) is a road sign word setting up this contradiction, so predict something like Oddly or Strangely. (A) paradoxically is correct. Predictably, (B), is the opposite of the prediction. Impetuously, (C), describes quick and thoughtless behavior, and while the people in this group demonstrate inconstancy in their support for the candidate, there are no clues to indicate they are making rash judgments.

The second blank is connected to "most likely to vote for the candidate" by the straight-ahead road sign "and," so predict that this demographic group was active or strong in its support in online forums. (F) matches this prediction since vociferous means “very loud” or "insistent." Tacit, (D), means “unspoken,” which would be the opposite of the prediction. Equivocal, (E), means “misleading and vague,” which may describe the pre-election survey data, but the word in blank (ii) must describe the people and these individuals expressed a positive view of the candidate. The word in the final blank will describe the "nature" of online polls, and this is described after the colon. Even though they generate "seemingly objective" data, they can be inaccurate—and inaccurate is a good prediction. (G) is correct because something that is specious is "misleading." Acerbic, (H), means "harsh" or "severe," and mutable, (I), means "changeable." Although people may behave differently on election day than indicated in pre-election polls and perhaps be considered "changeable," the word in the third blank describes the polls, not the people surveyed.