2007-02-01 : As the triggered ability resolves, the active player gets the option to perform the action. If that player declines, the next player in turn order gets the option. As soon as any player performs the action, the spell is countered, but the remaining players still get the option. If all players decline, the spell remains on the stack.

2007-02-01 : When this spell is cast, its “when you cast” ability triggers and goes on the stack on top of it.

2013-07-01 : A player can’t choose to sacrifice a creature unless they actually control a creature that can be sacrificed. For example, if the action were “discard three cards,” a player with two or fewer cards in hand couldn’t take the option to counter the spell.