nob gag

The biology professor tells his students, "Before I start today's lecture, I want to see if you have been keeping up with the readings." Calling on one girl, he asks, "Amanda, what organ of the body expands to ten times its normal size when excited?" Amanda turns the color of a wet sunset, drops her eyes in embarrassment and is unable to reply. Professor asks, "Sally, do you know the answer?" Sally says, "It is the pupil of the eye, sir." Professor says, "Very good Sally." Turning to Amanda, he adds,"Now, Amanda, I have three things to say to you: one, you have not done your homework; two, you have a dirty mind; and three, you're in for a big disappointment.

as read in here