"Yes," she said."I can't find the expiration date."
Before I could start my first job right out of college,I had to present evidence that I was a U.S.citizen,so I brought a driver's license and birth certificate.The clerk looked at my driver's license and copied down some information.She then picked up my birth certificate and gave it a good,long look."Is something wrong?" I finally asked.
"Yes," she said."I can't find the expiration date."
这是一个英语笑话,但是最后一句说明什么问题呢?