I teach Chinese to a mixed group of students who come from the U.S.A., Russia, Japan and Korea. One day I told my class a joke but received no response except from a Japanese girl who was smiling.
　　“I am sorry that most of you missed my joke,” I said and turned to the girl student.
　　“Miss Japan, would you please tell us what in my joke made you smile?”
　　“Sorry —, I can't, Sir. I was smiling to please you,” she replied, still smiling.