Here's the
official explanation provided by the GMAC for this question:
The sentence describes two alternatives presented to a hospital patient needing surgery: (1) waiting a few weeks for the surgery; (2) going to surgery immediately. These options are best described by conjoining two parallel phrases using
or. It is unclear whether option (1) implies that a choice between waiting two weeks and waiting three weeks was for the patient to make.
Option A: This version creates a structurally flawed sentence. For example,
choice of cannot fit with the direct-question form
would he … surgery. This form is not parallel with the verbal-noun form
waiting.
Option B: The
unless clause does not clearly express the alternatives constituting the choice (if the sentence were addressed directly to the patient, of course, a choice might have been conveyed by saying: “you can wait two or three weeks—unless you’d like to proceed to surgery immediately.”) The adverbial clause
unless … surgery can be read as modifying the verb
was given rather than
wait; this wording confusingly suggests that the patient may have been offered a choice between waiting two weeks and waiting three weeks, as well as the option of having surgery immediately.
Option C: The phrasing using
or does not satisfy parallelism requirements and creates a structurally flawed sentence. The phrasing
he would proceed is not parallel with
waiting. The wording confusingly suggests that the patient may have been offered a choice between waiting two weeks and waiting three weeks.
Option D: Correct. This version is grammatically correct and satisfies the parallelism requirement for use of
or; the verbal form
proceeding is parallel with the verb form noun
waiting.Option E: This version is ungrammatical and fails to satisfy the parallelism requirement for use of
or; proceeding is not parallel with
to wait.The correct answer is D.
Please note that I'm not the author of this explanation. I'm just posting it here since I believe it can help the community.