.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 were ready to start.3） am/is /are being done 现在进行时例A new cinema is being built here4） was/were done 一般过去时例I was given ten minutes to decide whether I should reject the offer.5） had been done 过去完成时
