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

　　The whole class chorused "Good Morning".

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

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

　　"Well," he said. "When I say 'Good Morning' to a class, if they are freshmen they say 'Good Morning' too. If they are sophomores2, 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."

　　一天，工程系的主任走進一間教室說：“早上好。”

　　全班同學(xué)異口同聲地回答：“早上好。”

　　“你們是大一新生吧？”主任問道。

　　班級里一個膽子比較大的同學(xué)問主任是如何知道的。

　　“嗯，”主任說，“當(dāng)我說‘早上好’的時候，假如是大一的新生，他們也一定會說‘早上好’的。假如他們是大二的學(xué)生，他們會輕輕地合上課本，然后集體看著我。大三的學(xué)生則會抱著書本，抬起頭看我一眼，然后又繼續(xù)讀書。大四的學(xué)生則根本無視我的存在，一直看著書。至于研究生班的學(xué)生，我向他們‘問早上’好，他們就會把這句話寫在筆記本上。”