The 6th grade science teacher asked her class, "which body part increases to 10 times its size when stimulated?"
No one answered for a long time till little Mary stood up, angry, and said the teacher should not be asking 6th graders a question like that. She was going to tell her parents, who would tell the principal who would fire the teacher!
The teacher ignored her and asked the question again, "which body part increases to 10 times its size when stimulated?"
Finally Billy stood up and said that the body part that increases 10 times its size when stimulated is the pupil of the eye.
The teacher said "very good, Billy," then turned to Mary and said, "As for you, young lady, I have three things to say:
1) you have a dirty mind,
2) you didn't read your homework, and
3) one day you will be very, very disappointed