The attractive young Sarah was about to go to bed with her new boyfriend Joe, when she burst into tears.
"I'm afraid you'll get the wrong idea about me," she said between sobs.
"I'm really not that kind of girl!"
"I believe you," Joe said, as he tried to comfort her.
"You're the first one," Sarah replied.
"The first one to make love to you?" Joe asked.
"No, silly," she replied. "The first one to believe me!"