GMAT idioms and sentence corrections can be hard to approach, particularly for those for whom English is not their first language (and even for those for whom it is). Unlike the reading comprehension section, these parts of the test the taker’s ability to recognize and correct constructions that are not “literally derived from the most basic rules of grammar and vocabulary.”
The Official GMAT blog has even addressed this issue about GMAT idioms and sentence corrections. They assure test takers–a growing number of whom are international–that this isn’t “an American test.”
“As the GMAT exam has expanded globally and been taken by more students from around the world, GMAC has continually made extra efforts to ensure that newly introduced GMAT items do not depend on familiarity with distinctively American expressions and usages. We have taken steps all along the way to ensure global fairness and appropriateness.”
As far as grammar goes, they reinforce the idea that even though many answers may “seem” right, “the correct answer is the sentence that is most “effective,” the sentence that better expresses the idea.”
Another post about GMAT idioms and other grammar questions at Beat The GMAT recommends that test takers really trust their ear when faced with especially difficult questions: those “rare idioms, awkward phrasing, and suspicious pronouns [that are designed] to keep you off balance.”
They encourage you to really “forget the rules, and pretend that you’re saying the sentence to your best friend. Pick whichever choice makes you feel the least ridiculous.” To help drive this point home, they walk through a particularly gruesome question that deals with many issues.
Even though the point of that specific post is to help you feel comfortable making a decision to trust your ear, the blog is also quick to point out the importance of being familiar with GMAT idioms and correct pronoun usage. Being able to do both is important, whether you are applying abroad or to Washington DC MBA programs.