[Thankfully, he's not paying attention - he's watching all of the work that goes into a cappuccino, wondering if it'll prove to be worth so much effort. He does glance at her in surprise when she answers his question so quickly, though, although he's still not equipped to understand that smile.]
Either you're very intelligent, or that was yet more common knowledge that I had yet to learn. Can I trust you to say which it is? [Playful.]