When you narrow down the options to the two most likely answers, assuming of course that your elimination of the other two were correct, you have a high chance of passing. 

Each MCQ's answer options has "statistical characteristics" within them (says AICPA), meaning that they have different weightings assigned.  In other words, more marks are awared to the two most likely answer options than the other two that were eliminated. So your selecting the two closest possible answers puts you in the high probability range of passing. This is what differentiates a passing candidate from a failing candidate. 

That reminds me why I got 44 in my last sitting for FAR.  I had selected the answers which were the lowest weigtings (really the least possible answers). I guess I could blame it on my lack of knowledge of the concepts/rules.  I couldn't even narrow down the answers to the two most likely ones.

So if a candidate, by the process of accurate elimination, narrows down the answer options to the two most likely ones, puts him in a better position to pass.

Therefore, one should not see it as outright failure when they cannot tell which one to select from the two and have to resort to guessing. It's a good sign, a sign that you will pass if your process of eliminations were correct.  You will end up really surprised like e_rock494 because accurate eliminations were employed.

So passing any CPA section boils down, basically, to two important things:

1. Know your rules/concepts well before going into the exam.
2. Eliminate the two least possible options.

Then select - don't feel bad if you are undecided and resort to guessing - it's a good sign. You should be fine.