原文If a creature an opponent controls can't attack for some reason (such as being tapped or having come under its controller's control that turn), then it doesn't attack. If there's a cost associated with having it attack, its controller isn't forced to pay that cost, so the creature doesn't have to attack in that case either.
原文If a creature an opponent controls doesn't qualify for any of the above exceptions and can attack, it must attack a player other than you if able. If the creature can't attack any of those players, or if there are no such players, it must attack you or an opposing planeswalker.