GMAT loves to test different versions of idioms that are correct. Only one correct idiom will fit into the context of the sentence.
combine A and B
combine A with B
The only way to see which one is correct is to see whether you are comparing similar or unlike items.
However, this question is not really about idioms. It is about the subjunctive mood.
directive verb + "that" + subject + base verb
(of both public and private employers) that pay be
the same for jobs historically held by women as for jobs requiring comparable skill that are usually held by men.
i solved this one a few weeks ago.
http://www.gmatclub.com/phpbb/viewtopic ... n+province