Who's the printer?

The professor was giving the final lecture of the term. He spoke about students work and asked them to prepare for the final examination well. He said, "The examination papers are now in the hands of the printer. Are there any questions?"
There was silence. But suddenly a voice from the rear sked, "Who is the printer?"

谁是印刷工？ 　　　
　　　
教授在给学生上本学期的最后一堂课，他讲了一些关于学生的作业情况，然后要求学生好好准备期末考试。他说道，“考卷已经在印刷工手里了。还有什么问题吗？”
教室里一片寂静。突然从后排传出声音问道：“谁是印刷工呀？”