例如:—Who is he?—He is Tom’s father.—What’s this?—It is a book.are用于第二人稱單、復(fù)數(shù)和第一、三人稱的'復(fù)數(shù)。例如:You are a student. We are students, too.

　　2、am,is和are可以幫助構(gòu)成否定句和疑問(wèn)句。在am,is或are之后加上not,即將句子變成了否定句；把be動(dòng)詞提到句首,即將句子變成了疑問(wèn)句。

　　例如:I’m from China. →I’m not from China. →Are you from China? (對(duì)I am的提問(wèn)比較特別)

　　He’s thirteen years old.→He isn’t thirteen years old.→Is he thirteen years old?

　　They are policemen. →They aren’t policemen. →Are they policemen?

　　看了以上例句,一定要注意am,is和are在句中的縮寫形式。另外,am,is,are與this,these,those在一起時(shí)一般不縮寫。

　　3、be也可以位于句首,表示向別人提出要求。例如: Be a good student! 做個(gè)好學(xué)生！