The teacher had given the class an assignment. He stresses the importance of this particular assignment, and that no excuses will be accepted except illness (with a medical certificate) or a death in the immediate family (with a note from that member). A smart-ass student pipes up:
"What about extreme sexual exhaustion, sir?"
The class breaks up laughing, and when they settle down the teacher
"Well, I guess youll have to learn to write with your other hand."