A desperate young husband phones the doctor: “
Doctor, doctor, my wife and I are brown-haired while our son has red hair, how is this possible?”
The doctor thinks about it for a few seconds and then asks: “
How often do you and your wife have intercourse?”
Embarrassed, the young man replies: “Once a year more or less…”
“Here’s the answer!”
“Meaning what?”
“The rust, it’s the fault of the rust!”
