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A lady walks into the drugstore and asks the pharmacist for some arsenic.
"Ma'am, what do you want with arsenic?"
"To kill my husband."
"I can't sell you arsenic to kill a person!"
The lady lays down a photo of a man and a woman in a compromising position.
The man is her husband and the woman is the pharmacist's wife.
He takes the photo, and nods.
"I didn't realize you had a prescription!"