Here's the
official explanation provided by the GMAC for this question:
The sentence—which is in order in its present form—suggests that, because he had been imprisoned, William Henry Porter was seeking anonymity when he chose the pseudonym O. Henry. The verb
seek has several different meanings; here, it means
try to gain, a transitive meaning that requires a direct object.
Option A: Correct. The past-continuous form
was seeking indicates a process; the simple-past form
chose indicates an action taken at a particular point in time in that process. The noun
anonymity is the direct object of
was seeking.Option B: This answer choice is wordy and unnecessarily awkward. The noun clause
that he … chose is unidiomatic as a direct object of
was seeking.Option C: The preposition
for is unidiomatic in this usage of
seek; here,
was seeking should have a direct object (that is, should not be immediately followed by a preposition).
Option D: This answer choice conveys an idea different from the one most likely intended. As written, it means something like
tried to remain anonymous while choosing. The phrasing
in the choosing of is unnecessarily awkward and wordy.
Option E: The verb form
sought suggests a single action rather than a process. The meaning of this version is probably not the intended meaning; it is best read as meaning
aimed to be anonymous insofar as he chose.
The correct answer is A.
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.