主要在以下句型中：
在主系表句子中： 主系表－－－系主表? He is a student. －－－Is he a student?
在现在与过去进行时态 中： 主+be+动词ing+其他
The boys over there are playing basketball. －－－Are the boys over there playing basketball?
I was doing homework when the bell rang. ----Were you doing homework when the bell rang?
在一般现在时或过去时的被动语态中： 主+be+动词过去分词+其他
The car was invented in 1876. Was the car invented in 1876?
还有现在进行被动语态中.望采纳!谢谢!