The dean of Engineering had once walked into a class, and said "Good Morning.”

一天工程系的主任走进一个班，说道:“早上好。”

The whole class chorused" Good Morning”

全班齐声回复:“早上好。”

"Hi，you are freshmen¹ aren’t you?" he asked.

“你们是大一的吧?”主任问道。

One student bolder than the others asked him how he knew.

一个胆子比较大的同学问主任是怎么知道的。

"Well，”he said. "When I say‘Good Morning' to a class，if they are freshmen they say Good Morning' too. If they are sophomores，they quietly fold their papers away，and look at me. A class of juniors will look at me over the top of their papers, and then get back to them. A class of seniors will ignore my greeting, and keep reading the papers. When I say `Good Morning' to a class of graduate students, they write it down.”

“嗯，”主任说，“如果是大一的新生，当我向他们问早上好的时候，他们也一定会说‘早上好’的。如果他们是大二的学生，他们会轻轻地合上课本，然后集体望着我。大三的学生则会从书本上抬起头看我一眼，然后马上又继续读书了。大四的学生则会对我视而不见，继续看书。至于研究生班的学生，我向他们问早上好，他们就会把这句话写在笔记上。”