A male teacher in a girls school asked: "Which part of the body expands to ten times its usual size when stimulated"
One girl, Mary blushed furiously and said: "Sir, how dare you ask such a question.
I will complain to the head master."
He called for another volunteer. Lily spoke up: "Sir, the answer is the iris."
"Very good, Lily," the teacher said, adding: "Mary, I have three things to say."

1) You have not done your homework.
2) You have a dirty mind.
3) One day you are going to be bitterly disappointed.