[hypothetical on] If FED adopted zap-10, and this was in the last minute of the 2nd quarter, A would have the option to choose zap-10, because B's foul prevented the clock from starting (It was already stopped due to the enforcement of A's OH). [hypothetical off]
Without zap-10, B would have the option, because B was originally the offended team. If B declines their option, A gets to choose.