Here's the
official explanation provided by the GMAC for this question:
The sentence suggests that it is fairly common for mystery writers to adopt a pen name in order to establish a reputation outside their usual genre. The underlined portion, however, has significant flaws.
Option A: The impersonal use of
it is unnecessary here: the thought underlying the wording
it is fairly common to do so would be more clearly and more economically expressed by such wording as
doing so is fairly common. The adverbial modifier
among mystery writers misleadingly applies to the verb
do rather than to the adjective
common and could appear to mean that some writers adopt pen names while they are in a group of mystery writers. The phrase
do so is probably intended to be a surrogate for
adopt pen names … genre, but it is unclear what idea is meant to be expressed by
adopt pen names among mystery writers.
Option B: The use of
that is informal and somewhat unclear; could it refer, for example, to writers’ establishing a reputation outside their usual genre? But the verb phrase
do that can be read as a surrogate for
adopt pen names … genre. The adverbial modifier
among mystery writers could be read as applying to the verb
do rather than to the adjective
common. The idea
adopt pen names among mystery writers is unclear.
Option C: The use of
that is informal and somewhat unclear; could it refer, for example, to establishing a reputation outside their usual genre? But the verb phrase
doing that can also be read as referring to
adopt[ing] pen names … genre.Option D: Correct. Even though the noun phrase
a practice … writers clearly and economically refers to the practice by some writers of
adopt[ing] … genre. The only practice mentioned in the main clause is the practice of adopting pen names for a particular purpose, so the intended reference of
practice is clear. The word
that is a relative pronoun referring to
practice. The adverbial phrase
among mystery writers modifies
common.Option E: The word
and is not needed following the semicolon and would be better omitted. The impersonal use of
it in its first occurrence is unnecessary and especially undesirable given the second occurrence of
it. What
it refers to in its second occurrence is undesirably vague. The adverbial phrase
among mystery writers modifies the verb
do. This yields the unclear idea
adopt pen names among mystery writers.
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.