Many, many years ago..during inorganic chem class frosh year of college..2nd lecture of the semester..taught, BTW..by a very distinguished professor, not a GA..50 or so in the lecture hall..he walks in..asks a question of the class..of course no one volunteers..he looks down at us..says.."either all of you are geniuses, and know all the material, and think the question is beneath you, or you are all cretins, and haven't bothered to even open the book. In either case, there's no point in wasting my time, and yours.."..and he walked out of the room..
needless to say..from that day forward..all of us were vigorous paticipants in the discussion.
Naturally, the next class he calls on me and I had not read the case for that day. I take a pass, and he proceeds to rail on me.
LOL...lesson learned.