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Visitorsarerequestednottotouchtheexhibits.
2)has/havebeendone现在完成时
例Allthepreparationsforthetaskhavebeencompleted,andwe'rereadytostart.
3)am/is/arebeingdone现在进行时
例Anewcinemaisbeingbuilthere.
4)was/weredone一般过去时
例IwasgiventenminutestodecidewhetherIshouldrejecttheoffer.
5)hadbeendone过去完成时
例Bytheendoflastyear,anothernewgymnasiumhadbeencompletedinBeijing.
6)was/werebeingdone过去进行时
例AmeetingwasbeingheldwhenIwasthere.
7)shall/willbedone一般将来时
例Hundredsofjobswillbelostifthefactorycloses.
8)should/wouldbedone过去将来时
例Thenewswouldbesenttothesoldier'smotherassoonasitarrived.
9)shall/willhavebeendone将来完成时(少用)
例TheprojectwillhavebeencompletedbeforeJuly.