Video Explanation

Text Explanation

Here, the gerund begins the sentence and is (or should be) the main subject of the entire sentence.

Split #1: on the Sentence Correction, the GMAT adores the "not only P, but also Q" construction: only choices (A) & (B) have this correct idiom. Incorrect variants include "not only … and" (choices (C) & (E) make this mistake) and "not only … and also" (choice (D) makes this mistake).

Split #2: one mistake involves the placement of the common word "for" in parallel structure The word "for" can either appear once before and outside of the parallel structure — "for not only P but also Q" (no answer choice has this) — or it can be repeated in each term of the parallel structure —- "not only for P but also for Q" (choices (B) & (D) have this correct). It is a classic GMAT Sentence Correction mistake to have the common word once outside and once inside, as in "for not only P, but also for Q" (choices (A) & (C) have this incorrect construction). Choice (E) blatantly violates the parallelism, so that's an even bigger problem!

Split #3: The "ability" idiomatically is followed by an infinitive — the "ability to do something" (choices (B) & (C) get this correct). A common idiomatically incorrect construction involves the word "ability" + "in" + [gerund] — "ability in doing something" (choices (A) & (D) make this idiom mistake). Choice (E) avoids this particular issue by blatantly violating the parallel structure, again, a much larger problem.

Those three splits are already enough to isolate choice (B) as the only possible correct answer.

Split #4: the missing verb mistake. If you notice, choices (A) & (C) are not complete sentences — the subject "getting" does not have its own verb anywhere in these sentences. Choices (B) & (D) provide the main verb "has" for the main subject "getting." Sentence (E), with it substitution of "that" for "which" has a particular bizarre structure — technically, in version (E), everything from "the depth of that" to the end would be a complete sentence, but then the whole first part is odd gerund phrase that sticks out awkwardly like a sore thumb and doesn't fit with the rest. If we fixed the other mistakes in choice (E), we could rectify this problem by constructing two separate sentences following this layout: "Getting adequate sleep, a full eight hours every night, is important. The depth of this sleep will be …." That would be a possibility in real-life editing. In the GMAT Sentence Correction, though, you have to stick to one sentence, so (E) is out.

The only possible answer is (B).