（1）强调动作的接受者：America was discovered by Columbus.
（2）不知谁是动作的执行者：You are wanted on the phone.
（3）作客观说明：It is said that the meeting has been put off.（经典句型）
2．主动变被动的基本方法：（说起来容易，掌握起来需要用心！）
（1）主动语态中的宾语变为被动语态的主语。
（2）谓语动词变为由“be + 过去分词”的形式，配合时态作相应变化。
（3）主动语态主语置于介词 by之后，如无必需，则省略。
（4）不及物动词没有被动语态。
现 在 do (does) →am / is / are + done
We keep the piano in the living-room.
→The piano is kept in the living-room.
过 去 did→was / were + done
They built the bridge in 1980.
→The bridge was built in 1980.
将 来 shall shall
will do → will + be + done
He will read the book tomorrow.
→The book will be read tomorrow.
现在完成 have have
has done → has + been + done
We have delivered the newspaper.
→The newspapers have been delivered (by us).
过去完成 had done → had been done
She had seen the film before she came here.
→The film had been seen before she came here.
将来完成 shall shall
will have done → will have + been + done
By the end of this term we shall have finished 80 texts.
→By the end of this term 80 texts will have been finished.
现在进行 am am
is doing → is + being + done
are are
They are drawing the picture.
→The picture is being drawn by them.
过去进行 was doing → was + being + done
were were
He was reviewing their lessons at this moment yesterday.
→Their lessons were being reviewed at this moment yesterday.
情态动词 may may
can can
must must
should do → should + be + done
ought to ought to
used to used to
You must write an article on the subject.
→An article must be written on the subject.
发表于 2016-7-11 22:29:34