Derek's eyebrows lift at the question because, even in his increasingly inebriated state, he can tell that that's something of a challenge and she's kind of thrown down a gauntlet of sorts. He's just not sure what the "right" answer would be. So he narrows his eyes at her, giving her a playfully suspicious look.

"What if I choose wrong? You gonna leave me to drink alone like a pathetic loser?" he asks.