In no other historical sighting did Halley's comet cause such a worldw

I’ve always thought that this is one of the toughest comparison questions in any of the last eight editions of the official guide. (Related: my bookshelf is a hot, hot mess.) More than one answer choice sounds perfectly fine to me, and several of them would probably be acceptable in real life. But on the GMAT? We need to be unreasonably anal and literal and precise. Fun times.

We also covered this one in part 2 of our YouTube webinar on comparisons, so feel free to head over there if you prefer your explanations in video form.

There are two ways to think about why (A) is wrong. First, we could think about what, exactly, is being compared: “in no other historical sighting did Halley’s comet cause such a worldwide sensation as ________.” The heart of the question is that we’re trying to compare what happened in other historical sightings to what happened in 1910-11. So to keep the comparison even, it makes more sense to fill in the blank above with “in its return of 1910-11.” And that’s answer choice (C). We’ll get to that one shortly.

The second tool that’s helpful here: the helping verb “did” can play a variety of roles in English, but in this case, it’s basically trying to replace another verb. Think of it as analogous to a pronoun, except that it refers to a verb instead of a noun. And that means that we can replace “did” with the verb phrase that it refers back to: “cause” (or "caused", if we take some minor liberties with the verb tense). So we have: “In no other historical sighting did Halley’s comet cause such a worldwide sensation as caused its return in 1910-11.”

That’s pretty ridiculously ugly. (A) is out, whichever way you prefer to think about it.

I can’t make any sense of why we would use “had” here. I don’t really even understand what it means when it’s used by itself: I guess the sentence is trying to say “… as its 1910-11 return had caused”? Except that there’s no good reason to use past perfect here, and there’s no good reason to just hallucinate the word “caused” in that situation.

Plus… well, the heart of the comparison needs to revolve around the phrase “in no other historical sighting”, as discussed under answer choice (A). So (B) is gone.

Bingo! I know that I’m repeating what I wrote for answer choice (A), but here’s the beginning of the sentence again: “in no other historical sighting did Halley’s comet cause such a worldwide sensation as ________.” The heart of the question is that we’re trying to compare what happened in other historical sightings to what happened in 1910-11. So to keep the comparison even, it makes more sense to fill in the blank above with “in its return of 1910-11.”

And that’s exactly what (C) does. Let’s keep it.

You can use the same argument for (D) as we did for (A): if “did” replaces “caused”, this makes no real sense. “In no other historical sighting did Halley’s comet cause such a worldwide sensation as its return of 1910-11 caused.” That’s not the very worst thing, but it certainly isn’t great – and it’s definitely not capturing the essence of the comparison as sharply as (C). So we can ditch (D).

(E) isn’t completely horrible, and I’d be fine with this in real life. But again, (C) does a much, much better job of capturing the essence of the comparison. So (C) is our answer.