Here's the
official explanation provided by the GMAC for this question:
This sentence fails because of poor word choice:
undergoing being converted is as redundant as it is awkward. The process of
being converted does not need to be shown since
undergoing already contains the idea of process. To complete the sentence grammatically,
undergoing should be followed by the noun
conversion rather than the phrase
being converted. When only two alternatives are possible, to sign or not to sign,
whether (or
whether or not) is properly used rather than
if.
Option A: Being converted is redundant and awkward;
if is incorrectly substituted for
whetherOption B: Being converted must be replaced by the noun
conversion;
whether must be followed by the concise infinitive
to signOption C: Being converted must be replaced by the noun
conversion;
whether must be followed by the concise infinitive
to signOption D: Whether should be used in place of
ifOption E: Correct. In this sentence, the noun
conversion grammatically completes the phrase begun by
undergoing, and
whether is correctly followed by
to sign.
The correct answer is E.
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.