Mrs. Smith goes to the doctor's office to collect her husband's test results. The lab tech says to her，

"I'm sorry, ma'am,  but there has been a bit of a mix-up and we have a problem.

When we sent the samples from your husband to the lab, the samples from another Mr. Smith were sent as well and we are now uncertain which one is your husband's.

One Mr. Smith has tested positive for Alzheimer's and the other for AIDS.
We can't tell which is your husband. "

"That's terrible. Can we do the test over?"

"Normally，yes. But you have an HMO，and they won't pay for these expensive tests more than once."

"Well,what am I supposed to do now? "

"The HMO recommends that you drop your husband off in the middle of town. If he finds his way home, don't sleep with him."