2020天津公安消防考军校考试：语法总结（34）

　被动语态讲解

　　(一)、被动语态的构成形式

　　1. 被动语态的基本时态变化

　　被动语态通常为十种时态的被动形式, 被动语态由be+过去分词构成，be随时态的变化而变化。以do为例，各种时态的被动语态形式为：

　　1) am/is/are +done (过去分词) 一般现在时

　　例Visitors are requested not to touch the exhibits.

　　2) has /have been done 现在完成时

　　例All the preparations for the task have been completed, and we're ready to start.

　　3) am/is /are being done 现在进行时

　　例A new cinema is being built here.

　　4) was/were done 一般过去时

　　例I was given ten minutes to decide whether I should reject the offer.