Prof has a seating chart and makes mysterious marks on it when she calls on you.
You only read one case from the assignment, so you need to strike preemptively.
You didn't read any of the cases from the assignment, and Prof just asked the "Do you guys think that's fair?" question.
Prof has been begging someone to answer the question for more than 60 seconds, and he's a likable guy.
Prof has been begging someone to answer the question for more than 60 seconds, and he's getting pissed off.
If you don't answer a question, you'll nod off.
Everyone around you raised their hands, so you have to assume that Prof just asked a survey question (eg, "How many people think...?").
You had a few beers for Happy Hour before class.
The buddy sitting next to you just got cold called, and you owe him one.
You're a 2L.