Ties are worn around the base of the neck, and the neck is the flexible thin part that connects the head. I see position A as being well below the flex point, which would be like wearing the tie low on the shoulders. That's why I would prefer it at the bottom end of the joint, position C. One could reasonably argue that anything above where the body narrows down towards the neck is part of the neck, in which case A would also make sense.

Semantics on where a neck starts aside, position B is clearly at the top of the neck and is therefore just nonsense not even worth considering.

Also position C lets the tie hang neatly down the front of the body as it should, rather than dragging the ground or dangling loosely in midair.