The teacher gives a short, flat answer ("Not much.") and stays quiet — student must revive the conversation with a new question or topic.
The teacher suddenly mentions something unexpected ("Actually, I'm moving to another city next month.") — student must react genuinely and ask at least two follow-up questions.
Mid-conversation, the teacher abruptly changes topic ("Anyway, forget that — did you see the game last night?") — student must follow the switch naturally instead of getting stuck on the old topic.