Just a few thoughts here (with apologies to students for turning this into a debate among instructors!):
*As Mitch mentioned, there are exceptions to most rules in the English language, so I'd be careful with phrases like "The GMAT will always..." and "The GMAT will never..." unless it's a mathematical/logical/grammatical certainty that what you're saying the GMAT won't do is absolutely incorrect. The forums and blogs love to throw out "The GMAT prefers" and "the GMAT will never" but GMAC itself doesn't confirm/deny any of that, and its responsibility is to create fair, effective assessments so if something is commonly and accurately used in language I wouldn't write it off as impossible to appear on the test. (And as Mitch showed, there's proof in this case that Ceilidh's primary objection to the problem in question is actually something that GMAC has tested).
*Not to go personal attack at all, but in classic Critical Reasoning style your conclusion "every single answer is grammatically incorrect" isn't really supported by your premise "D...is incredibly awkward. I'd argue that it's idiomatically incorrect." For one, "awkward (but correct)" is actually a testmaker technique on challenging problems, forcing examinees to think critically about the meaning and structure of a sentence. (This article shows that off pretty well, using an official GMAT problem as the demonstration:
https://poetsandquants.com/2013/06/20/he ... only-hope/) And, of course, GMAT correctness doesn't come from "a 99th percentile scorer / reputable GMAT instructor could make an argument that it's incorrect." Most of us who have been doing this for a while would still, if we're being honest, have to see a few correct official answers and think "wow, I'd never say it that way but I guess they have a point (plus it's the only option that doesn't violate something major)."
*For this particular problem, if a linguistics PhD came to me and told me there was a slight idiomatic flaw with it I guess I wouldn't be shocked, but I'd be surprised. This sentence (along with I think at least most of the others you linked) came straight from a pretty reputable, well-edited/well-written publication. Knowing that the GMAT uses "interesting/unique" sentence structures (your classic anaphoras, asyndetons, and hyperbations like that above link mentions), we're always on the hunt for GMAT-style sentences with those strange structures so that our students are trained to deal with that kind of awkwardness on test day. That's especially important to us because, ever since the GMAT switched item writers from ETS to ACT in 2006, the trend has been much less "idiom/memorization" and much more about sifting through denser sentences to find meaning and structure (at least at the high end of difficulty). So if you do find our more-challenging problems to be a bit awkward...thank you - that's by design.
*And with that knowledge that the GMAT has evolved - particularly on the verbal side, with more logic and meaning on SC, more "practical" (plan/strategy, useful-to-evaluate) CR, shorter/denser RC - it's important for students to realize that newer, official problems are the best sources out there. Which tends to mean that the electronic resources (the newer resources like the Question Pack and GMAT Prep tests) are more current, and that problems that date back to the 10th or 11th edition Official Guide (which therefore were appearing on GMATs in the 1990s) are less useful for study. There's a lot of Sentence Correction practice out there that's modeled after those old questions, so one of our aims in recent years (so problems with serial numbers above maybe 06000) is to get plenty of "new-style" SC practice out there for students.
*Lest we forget the point of the forum, to help students with their questions and provide strategic guidance: Radbuz, if you're still reading this, your instincts were pretty good getting to D! And what makes D pretty tricky (and what made us do a double-take when reading this in print) is that "$453 million" is used as an appositive modifier there to further explain 13 percent (just like saying "Radbuz, a GMAT student, asked a great question..." in which "a GMAT student" is just a noun used as a modifier to explain more about you). That's an important part of tricky Sentence Correction - on hard problems the right answer may not be written exactly as you'd write it yourself, so you have to train yourself to seek-and-destroy the errors you know you can't live with and deal with the structural choices that you can live with.
