How to find out which audio stream is which?


I wanted to copy a movie that has 3 audio streams. I has AC-3/5.1, AC-3/2 and AC-3/2 which would be the director’s comments. Is there any way ahead of time in knowing which of the AC-3/2 streams is the movie and which is the director’s comments? I assume that since I do not have surround audio that I need the AC-3/2 stream and not the AC-3/5.1 stream.

I guess the above is not really super important since a AC-3/2 stream only uses 100mb of space, but still I would like know.