"Yeah," Harry said, looking up. He eyed Ron for a moment, as if he was trying to figure out what he'd been doing, and then decided it was useless. Maybe he could convince Ron to tell him if he tried again; five hundredth time would be the charm? Or maybe not. He supposed he should also stick to Hermione's rule to ask Ron a question, especially if he was going to hand over something as precious as the luck potion. "What'd I do to the troll in the bathroom with my wand, in first year?"
It was the first question that came to mind, and probably a stupid one, but they'd exhausted so many at this point. Anyway, it was better than no question at all.