例句：

　　He is a bus driver. ----- He was a bus driver.

　　am的過(guò)去式是“was ”，過(guò)去分詞是“been ”,主語(yǔ)為"I"；

　　例句：

　　I am a student. ---- I was a student.

　　are的過(guò)去式是“were”，過(guò)去分詞是“been ”。are是復(fù)數(shù)，主語(yǔ)用you， we ，they。

　　例句：

　　They are basketball players. ---- They were basketball players.