I'm working on a red instant and sorceries deck featuring Charmbreaker Devils. As I understand it, this ability:
At the beginning of your upkeep, return an instant or sorcery card at random from your graveyard to your hand.
is a triggered ability. So I should be able to use Strionic Resonator to copy it. How exactly does copying it work? Is there a chance that the same card in my graveyard is chosen twice, or will I always get two instants or sorceries back, as long as there are two to start with?