God Bless You?

What is the protocol when you are at the urinals next to a priest and the priest farts?   This happened at the wedding I was at over the weekend.   These are the options that went through my mind:

A) "God bless you"

B) "Nice out"

C) Look over, head nod

D) Return fire

I opted for C mostly because I did not have a fart on deck.  The priest, a very nice guy, nodded back and went to wash his hands.  Needless to say I was not ready for this situation but maybe next time I will have some ammunition to mount a solid counter attack.