一，主动语态改被动语态
　　把主动语态改为被动语态非常简单，可以遵循以下几个步骤：

　　1. 先找出谓语动词；

　　2. 再找出谓语动词后的宾语；

　　3. 把宾语用作被动语态中的主语；

　　4. 注意人称、时态和数的变化。

　　例：1. Bruce writes a letter every week. →A letter is written by Bruce every week.

　　2. Li Lei mended the broken bike this morning.→The broken bike was mended by Li Lei this morning.

　　3. He has written two novels so far.→Two novels have been written by him so far.

　　4. They will plant ten trees tomorrow.→Ten trees will be planted by them tomorrow.

　　5. Lucy is writing a letter now.→A letter is being written by Lucy now.

　　6. You must lock the door when you leave.→the door must be locked when you leave.
二，主动语态变为被动的几个特殊情况　　
      ① 有些动词在主动结构中，后面接不带to的不定式，但如果改为被动，则需把省略的to加上，这类动词有 [let, make, have,help]和感官动词[feel,see,hear,watch,look at,listen to]，如：The boss made my grandfather work 10hours a day.改成My grandfather was made to work for 10 hours a day.

　　② 含有宾语从句的主动结构变为被动，通常用it作为被动结构的先行主语，从句放在句子后面/也可采用另一种形式，这类动词有：know, say, believe, find, think, report等

　　③ 不是所有的主动句都可以变换成被动句，更不是所有的被动句都可以自由变换成主动句。虽然语法原则上允许主动和被动句的互相转换，但有的句子转换后会变成不通顺或不地道的英语句子。因此，在某些题目里，这也成为判断应该用主动还是用被动的依据。

　　例：At 5:05 p.m. on Saturday 19th July , there was an accident at the junction of the Main Street and Panda Road when a boy was knocked down off his bicycle by a delivery van. The boy was sent to St. Maria Hospital where he was treated for shock and a broken arm.

　　在这段文章里，a boy was knocked down off his bicycle by a delivery van这句被动句强调出读到文章的人最关心的事故的受害者。The boy was sent to St. Maria Hospital这句话则说明了孩子被送到医院的事实，至于是由谁（某个过路人？或肇事司机？）送的不重要。he was treated for shock and a broken arm这句被动句无须说出treat这个动作的发出者，因为在医院，伤病员自然由医务人员处理，无须罗嗦。这样，这段文章就重点突出，条理清楚了。

　　④ 有些动词可以有两个宾语，在用于被动结构时，可以把主动结构中的一个宾语变为主语，另一个宾语仍然保留在谓语后面。多是把间接宾语变为主语。这样句子自然些。直接宾语变为主语时，间接宾语要变为某个介词的宾语，介词to可以省略。如His father left him this house.改为This house was left (to) him by his father.

　　⑤ 有些动词虽为及物，但宾语并非是动作承受者，不能转换，这些动词有have, hold（容纳）,suit, fit, lack, become（适合）contain, cost, last, mean, suffice（足够）等。

　　⑥ 当直接宾语为反身代词、相互代词或宾语前有指代主语的物主代词时不用被动，如I shook my head.我摇摇头。

　　⑦ 当宾语为同源宾语（与主句指同一人），动名词，动词不定式或一个从句时不用被动。如John enjoyed seeing the fil,.

　　⑧ 在一些固定说法中，有些名词和动词结合的固定说法，不能改We Chinese always keep our word.

　　⑨ 某些从不及物动词转化来的及物动词，直接宾语在表示动作的方式或效果时，这些动词在意思上起状语的作用，没有被动The girl kissed her boyfriend good night=The girl said good night to her boyfriend by kissing him.(这个女孩说了晚安并且亲了他的男朋友）

　　⑩ 表地点\处所\组织\长度\大小\数量\程度\抽象名词的词做宾语时不用被动.

　　⑪ 某些“不及物动词+介词”短语,walk into, listen to, sleep in, agree with, shake hands with, belong to, take part in, keep up with不能用被动。

　　⑫ 某些词用主动表被动：sell, miss, build, grow, look, smell, taste, sound, feel等
      亲爱的同学们啊，生活就是这么美好呀，明天带来的是某些不用被动语态的情况哦。。。
   1.A lot of things ____ by people to save the little girl now.
   A. are doing B. are being done C. has been done D. will be done
   
2. Do you think that the bridge ______ in a year?
A. would be completed B. will be completed C. had been completed D. is being completed