（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）谓语动词变为由“be + 过去分词”的形式，配合时态作相应变化。
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 will/shall do → will/shall + be + done
He will read the book tomorrow.
→The book will be read tomorrow.
现在完成 have/has done → have/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 will/shall have done → will/shall 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/is/are doing → am/is/are + being + done
They are drawing the picture.
→The picture is being drawn by them.< /p>
过去进行 was/were doing → was/were + being + done
He was reviewing their lessons at this moment yesterday.
→Their lessons were being reviewed at this moment yesterday.
情态动词 may may
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.
1. Since the first space mission, many communication satellites ________.
A. was launched B. are launched C. have been launched D. had been launched
2. What kind of advice ________ you?
A. has gave B. was gave C. had been given to D. has given
3. The slave ________ from morning till night.
A. madeto work B. was made working C. was made worked D. was made to work
4. The construction of the laboratory ________ by the end of July.
A. must be completing B. must complete
C. must have completed D. must have been completed
5. Your proposal ________ by the committee soon.
A. is discussed B. has been discussed
C. is going to be discussed D. will have been discussed
1. C 2. C 3. D 4. D 5. C