Hey RadiumBall,

Great question - and honestly I'd say that the very fact that you have to ask means you probably can't eliminate this choice based on the idiom. I'll offer this as a rule:

Only eliminate based on idioms that you know for 100% certain are incorrect; otherwise, look for a better reason, and then if all else fails compare the remaining choices against each other.

We're just not that great at idioms - they're often too case-specific or exception-to-the-rule based for us to process them. But think about it - why does Harvard Business School care whether you've studied more idiomatic grammar than I have? These questions are set up to test your decision-making and problem-solving abilities, so it they're well-written (and they are) there's going to be a way for the test to reward you for thinking systematically and analytically.


On this particular question, notice that choices C, D, and E all have pretty flagrant modifier errors in which the first half of the sentence does not logically modify the subject of the sentence. To me, that's a clue - I'm testing whether the modifier (which is kind of a comparison: whearas in one x is true and in the other, y is true...) is logical.

Here, choice B isn't perfectly logical or parallel - we're comparing "whereas the tubes..." to "birds have tubes". When compared directly with choice A, B is fairly unclear and awkward in its comparative structure, while A is crystal clear. That's why I'd eliminate B.



Ultimately, the takeaway is to get comfortable with the handful of idioms (as many as ---> correct; as many than ---> incorrect) that tend to come up frequently, but after those few idioms there are just too many for you to really become good at them, so focus your time and energy on the major error categories...that's a much surer path to success.