1. 不知道动作的执行者时。如：

This house was built two years ago.

2. 不必提出动作的执行者。如：

The old machine has already been repaired.

3. 强调动作的承受者。如：

The little girl is liked by everyone.

1. 一般现在时：am/is/are + 及物动词的过去分词。如：

① We should study English well because it _______ widely around the world.

A. is speaking     B. speaks      C. is spoken    D. was spoken

② Maria _______ at 6:30 every morning by her mother to get ready for school.

A. was woken up   B. woke up    C. wakes up    D. is woken up

2. 一般过去时：was/were + 及物动词的过去分词。如：

③ After the teacher, Tan Qianqiu’s story _______ on CCTV, many people are learning from him.

A. was reporting   B. was reported  C. reported     D. has reported

3. 现在完成时：has/have + been + 及物动词的过去分词。如：

④ The Olympic Park has already _______ in Beijing.

A. built           B. building     C. been built    D. to be built

4. 一般将来时：shall/will + be + 及物动词的过去分词。如：

⑤ The meeting _______ in Shanghai this coming Saturday.

A. has been held    B. was held     C. will hold    D. will be held

⑥ More than two schools _______ in the city next year.

A. are built        B. will be built    C. have built   D. were built

5. 含情态动词的被动语态：情态动词 + be + 及物动词的过去分词。其中的be不能再作任何变化了。如：

⑦ Old people must _______.

A. be spoken to politely  B. speak to polite  C. be spoken politely  D. speak polite

⑧ Food and drink should _______ to bring into the reading room.

A. allow              B. allowed        C. not be allowed     D. not be allowing

    (Keys: 1―8 CDBCDBAC)

首先将主动语态的宾语变为被动语态的主语，然后将谓语变为被动语态，最后将主动语态中的主语放在介词by的后面。如：

A lot of people speak English. →English is spoken by a lot of people.

在将主动语态变为被动语态时，要注意以下几点：

1. 含有双宾语的主动语态在变被动语态时，通常将指人的间接宾语变为被动语态的主语；也可将指物的直接宾语作为被动语态度的主语，但应在间接宾语前加上介词to(谓语动词多为pass, give, teach, bring, send, show, write等) 或for (谓语动词多为buy, make, draw, keep等)。如：

His aunt gave him a nice present yesterday.

→He was given a nice present by his aunt yesterday./A nice present was given to him by his aunt yesterday.

2. 感观动词或使役动词在主动句中其后的动词不定式不带to，但在变为被动语态时必须使用to。如：

I often hear Mary sing in the next room. →Mary is often heard to sing in the next room. 

3. 动词短语(“动词 + 介词”、“动词 + 副词”等)作谓语的主动句在变为被动句时，要注意不要遗漏动词后面的介词或副词。如：

We should take care good care of the old. →The old should be taken good care of.