Quote:
Isn't C ambiguous in that it looks as if who are women modifies law firms.
Best could have been "at law firms. the proportion of blah blah who are women blah blah". Please guide.
You always want to eliminate concrete errors first. Ideally, you'd never consider pronoun ambiguity at all, but if you did, it would be as a last resort. In this particular question, we have some nice, juicy decision points.
First, there's the question of whether "yet" is correct. I can write, "Despite Tim's tendency to shower once a month, he often smells of vanilla and lavender." Or I can write, "Tim tends to shower once a month, yet he often smells of vanilla and lavender." But I can't write, "Despite Tim's tendency to shower once a month, yet he often smells of vanilla and lavender."
Put another way, I can introduce a contrasting modifier with "despite," or I can connect contrasting clauses with "yet," but I can't do both. Eliminate (D) and (E).
Next, there's choice between "have" and "has" in the second part of the sentence. The subject is "proportion," which is singular, so we want "has." That leaves us with (C). No need to waste brainpower on the usage of "who."
Also, bear in mind that "who" has to refer to people. If you look at the relevant clause, "the proportion of
judges and partners at major law firms
who are women, the only element "who" could be describing is "judges and partners," so there's no real ambiguity here. (And again, even if there were, pronoun ambiguity alone is not a good reason for eliminating an answer choice.)
I hope that helps!