There is generally agreement that feral swine are unwelcome such as

Absolutely not -- C could never in a million years be correct. It tells me that "Asian carp... are far larger [than feral swine], [are] more vicious, and [are] mounted on four legs." And, in fact, given the preceding "but," you are telling me that those things (including, notably, being "mounted on four legs") do not apply to "feral swine."

No matter how well you parallel within that list of modifiers, this is totally insane. I never, ever want to see a giant, vicious, four-legged fish when I jump in a lake to go swimming!



There is such a thing as a "style comma" in the English language -- it is allowable to use a comma to improve the flow, clarity, and/or style of a sentence even if the grammar rules might not otherwise call for one. In this case, the comma seems to improve the clarity by creating a pause before "but far larger" to make clear that this phrase refers back to the swine (paralleling the modifier "like") and is not meant to parallel "threatening" and thereby refer to the carp.

As far as the clause-connection rule goes, then, think of it like this:

Connecting two independent clauses with just a conjunction and no comma -- always wrong.
Connecting two not-both-independent clauses with a comma and a conjunction -- sketchy, but sometimes okay. (See what I did there?)


Oh, and while I'm responding to things I've seen in this thread, I'll say this: The growing consensus among grammarians is that the word "like" is not strict -- it may refer to elements of the category in question, or to things that are only similar to the elements of that category. The GMAT will absolutely not be a stickler for a strict usage of "like." However, everyone agrees that "such as" is strict -- it can only refer to elements of the category in question. There's no problem with a GMAT question that calls "such as" incorrect when it does not properly describe elements of the category in question (e.g. "Asian carp are not a type of feral swine").


More generally, I want to say that the criticisms of this question have been vastly overblown. I grant that there might be some cultural bias in needing students to know what "swine" or "carp" are (even if you don't know both, knowing either one should be sufficient). And that is unfortunate. But it's actually pretty hard to create a plausible logical meaning for "such as" in any event -- even if you don't know what swine and carp are, how could something be, simultaneously, both an example of feral swine and far larger and more vicious than a feral swine? And if you do know at least one of those animals, then there's really nothing wrong with D; it is unquestionably the right answer here. (Actually, the "best" wrong answer is B -- it's only wrong because "threatened an invasion" is unidiomatic and a bit illogical -- and I don't see much of anyone arguing for, or picking, that one.)

(I say this, by the way, as a Veritas instructor but also someone who has not been afraid to call out weak questions from any company, including my own, when I see them.)