二、被动语态的用法

1.什么情况下用被动语态？

（1）当我们不知道或没有必要说出动作的发生者是谁时，通常用被动语态。这种情况下，句子中不带由by引起的短语。例如:

The book is written for children. 这书是为孩子写的。

（2）当动作的承受者是谈话的中心时通常用被动语态。这时可以带by短语。

This pen was given to me by Tom.这支笔是汤姆给我的。

（3）无必要或不愿说出动作的发出者。这种情况通常是出于礼貌方面的考虑。

Smoking is not allowed here.这儿禁止吸烟。

2.怎样变主动语态为被动语态

把主动语态变为被动语态，可分作三步进行:

第一步:找出主动句的宾语，把它作为被动句的主语。

第二步:将谓语动词的主动语态变为被动语态（助动词be+及物动词的过去分词）。变为被动语态时，时态不要变化。

第三步:将原主动语态的主语（若是人称代词，须变为宾格）放在介词by后边组成by短语，放到句子的后边。如果我们没有必要说出动作的发出者，by短语则可以不要。例如:

He often helps his brother.       (主动语态)

His brother is often helped by him.（被动语态）

【被动语态中考真题大练兵】

1. —Would you please tell Miss Li that she        as a volunteer for the 2008 Olympic Games?

—Of course. I will tell her tomorrow. 

 A. choose     B. chose     C. has chosen     D. is chosen

2. We        not to play computer games. 

 A. are told    B. have told    C. told    D. tell 

3. —Could you tell me whom the radio         by?—Sorry. I have no idea. 

 A. invents    B. invented    C. is invented    D. was invented

4. -Your hometown has changed a lot.

—Yes. Take a look at these tall buildings. They         last year. 

A. build    B. built    C. was built    D. were built

5. —Did you go to Kang Kang’s birthday?—No, I         .  

 A. wasn’t invited   B. didn’t invite    C. am not invited

6. An English speech         to the children tomorrow. 

A. is given    B. has been given  C. will be given

7. 根据汉语意思完成英语句子：

丢失的部件在船拖出水后被找到了。 

The lost parts                 after the ship was                of the water.

8. She used the knife to cut the fruit a moment ago.（改为被动语态）

The knife                 to cut the fruit by her a moment ago.

9. I sent a letter to you last month.（改为被动语态）

A letter                 to you last month.

10. 用括号内动词的适当形式填空：

The dog        （train）to understand different instructions for two years.

答案：

1~6 DADDAC 

7. were found; pulled out   8. was used   9. was sent   10. has been trained

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