I think the answer is C. We can eliminate A and D because they have the passive construction "problems faced by rural migrant workers" B and E both have an ambiguous pronoun. It's unclear what they refers to. C fixes both of these issues

IMO C

In choices A and D, couldn't 'they' also be referring to 'problems?'

in an assessment of the problems faced by rural migrant workers, the question....

ur OA is wrong...

the above phrase need "was" after comma than "iS" it's in past tense...
In assesing is for present ....use of "is" is corect..
IMO answer"a"..that's all..

and for ur kind inforamtion..
most of the options in GMAT which start with -ing are correct..
source OG-12

rahulsaroha wrote:in an assessment of the problems faced by rural migrant workers, the question....

ur OA is wrong...

the above phrase need "was" after comma than "iS" it's in past tense...
In assesing is for present ....use of "is" is corect..
IMO answer"a"..that's all..

and for ur kind inforamtion..
most of the options in GMAT which start with -ing are correct..
source OG-12

What is the OA then?

I found out a better explanation in beatthegmat itself. Please follow the link.

https://www.beatthegmat.com/sc-migrant-w ... 19303.html

For lazy asses, here is the explanation posted by tacosychelas -

In assessing the problems faced by rural migrant workers, the question of whether they are better off materially than the urban working poor is irrelevant.
(A) In assessing the problems faced by rural migrant workers, the question of whether they are better off materially than the urban working poor is irrelevant. Wrong because "a question" cannot assess a problem
(B) The question of whether the rural migrant worker is better off materially than the urban working poor is irrelevant in assessing the problems that they face. Wrong because "they" has no referent
(C) A question that is irrelevant in assessing the problems that rural migrant workers face is whether they are better off materially than the urban working poor. Wrong because the comparison of worker to worker is not parallel: they vs an urban working poor
(D) In an assessment of the problems faced by rural migrant workers, the question of whether they are better off materially than the urban working poor is irrelevant.
(E) The question of whether the rural migrant worker is better off materially than the urban working poor is irrelevant in an assessment of the problems that they face. Wrong because "They" has no referent