It's a combination of all of those.

If you smell like FART, but the deer has never associated a fart with a human before - you're fine. If you drop something out of your treestand, or your phone rings, you might not be DONE yet. The deer might look right at you, but if you're against a tree he might not know exactly what you are....

However, If you move, smell like fart and make a noise at the same time - GAME OVER. You can usually pull off one or two things from that list before you are BUSTED