In human hearing, subtle differences in how the two ears hear a given sound help the listener determine the qualities of that sound.
A. in how the two ears hear a given sound help the listener determine
B. in the two ears hearing a given sound help the listener in determining
C. in how a sound is heard by the two ears helps the listener determine
D. between how the two ears hear a given sound helps the listener in determining
E. between how a sound is heard by the two ears help the listener in determining

This is a GMAT Prep question

How to elimante this question

My first go was differences should have between . Even though "is heard " in E is passive I preferred that over A

But it is wrong. Correct answer is A ( My question for A is :help the listener determine should be help the listener to determine Otherwise A looks awkward.

Please explain

First, it shouldn't be "help the listener to determine" (although that is how lots of people would say it). You don't need the "to" - and, if you don't need it, then it's not going to be in the correct answer!

Be careful about deciding based upon what sounds good or bad. The test will fool your ear. Go based upon the specific rules you KNOW are true.

You may read an original sentence and think it sounds awkward (in fact, this will happen quite a lot!), but if you cannot point to a specific area that you KNOW is an actual grammatical error, don't eliminate A. It stays in as a possibility.

The in vs. between issue is an idiom. I say differences in X (just one thing) or differences between X and Y (two things). This sentence has one thing: how the two ears hear a given sound. So, I need "differences in." Elim D and E.

B says "differences in the two ears hearing" - that makes it sound like the two ears themselves are different (as in, they look different or something), as opposed to a difference in the way the two ears perceive a sound. That's not the original meaning (and doesn't even make a lot of sense), so elim B.

C says "differences... helps" - that's a subj-verb mismatch. Elim C. (you can also use this to elim D, if you haven't already eliminated it).

Only A is left. (And, usually this will be the process for getting yourself to A. There won't be anything wrong with it but you'll be suspicious of it b/c 80% of the time there IS something wrong with it, so you'll find some reason to say it sounds bad. But DO NOT eliminate A unless you can point to a specific error. Leave it in and test the others.)

Stacey, I am not sure how two ears is one thing? the difference between two twins is the height. --Is this wrong?

or do we say --Difference in two twins is their height.?

I am kind of confused please suggest.

re: your question above: you would say 'the difference between the two twins', because the two twins are two different people (as stacey points out above). more to the point, if you were actually differentiating between the ears themselves, you would indeed say: 'the difference between the two ears is...'

however, in this problem, you are not talking about the difference between the two ears; you're talking about the differences in one action - the same action - that's being performed by each of the two ears. therefore, you say 'the difference in the way the two ears perform this function.'

more illustrations:
the differences between the two twins are displayed in stark relief when they argue with each other.
the differences in the way the two twins play the violin are displayed in stark relief when they play duets together.

make sense?

Thanks for such a good explanation!!!!

Saurabh Malpani