The professor stands in front of his class naked, pointing to various charts, graphs and illustrations all on the topic of anal sex, the students are naked as well.
The professor, still naked, turns to face his class and says with a sigh, "Now, let's try this again. Shall we?"
He instructs the class to stand up and hold out their No. 2 pencils.
Looking around the lecture hall to make certain everyone was in compliance, the naked professor continues.
"Good," said the naked professor. "Now, on the count of three, we all drop our No. 2 pencils and bend over to pick them up."
Again, the naked professor pauses to look around, making sure everybody is in compliance before continuing.