At the doctors office

The husband waits outside while the doctor is diagnosing the wife.
She is still in the examination room when the doctor comes out to speak with the man.

"Sir, I have some bad news. Your wife has either Alzheimer's or AIDS."
"You can't tell which one? What am I supposed to do?"

"There is one thing that you can do... drive her out to the middle of nowhere and leave her there - if she comes back, don't fuck her."