The man matter-of-factly replied: "Those are called condoms, son. Men use them to have safe sex."
"Oh I see," replied the boy pensively. "Yes, I've heard of that in health class at school."
He looked over the display and picked up a package of three and asked: "Why are there three in this package?"
The dad replied: "Those are for high-school boys. One for Friday, one for Saturday, and one for Sunday."
"Cool!" said the boy. He noticed a pack of six and asked: "Then who are these for?" "Those are for college men," the dad answered. "Two for Friday, two for Saturday, and two for Sunday."
"WOW!" exclaimed the boy. "Then who uses these?" he asked, picking up a 12-pack.