The GM should make those options concrete in the situation. We should probably also reword that a bit - the optimal way is to have two options, both of which involve suspicion, danger, cost, or other downsides.
So, like, Niffin is picking a lock to get into the orcs' armory before the party storms their barracks. He gets an 8, so I think for a bit and say: "Just as the lock pops open, you hear an orc coming round the corner, you can smell his rancid breath from here. You've got a split-second before he's looking right at you, and it sounds like he's dragging one of those weird axes all the orcs have. Are you going to leave your tools and back off to hide (suspicion/cost) or try to take him out before he raises the alarm (danger)?"
Neither of these completely blocks him, it just puts another challenge between him and success. If he hides, the tools are probably gone, and the orcs are on guard. If he fights, well, that's dangerous, obviously. Either way, he got the lock open, there's just a complication.
Thanks for asking, by the way. Stuff like this goes right into the moves discussion section. :)