GMAT Verbal Section | Re: An proportion of women work/works????

Yes, it sometimes sounds awkward when used correctly, but that does not make it any less correct. If the writers at the GMAC want to consider that an "idiom," then that's fine, and of course GMAT students should take note. But that doesn't mean that I have to personally agree with them.

Although if I were forced to choose, I still would select Choice B (prioritizing correct grammar over awkwardness), I would say that there is no correct answer to this question, because Choice B is