被动语态的用法是什么?

be+过去分词

一. 定义：
被动语态,即不知道动作执行者或强调动作承受者的一种语态.例如中文常说：我被他打,这就是一种被动.但有时由于句子结构上的需要也要用被动,例如It is not unusual for workers in that region to be paid more than a month it 在句中作形式主语.而不定式to be paid more than a month是句子的逻辑主语.结合选项全句的意思是：“那个地方的工人一个多月后才得到工资是常有的事”.
二 构成：
be+past participle(过去分词)(简称P.P.)（+by+动作执行者）（过去分词的概念见上课）
三. 转换
当主动语态要被改成被动的时候,我们把原句的宾语提前,作为改句的主语,主语后置,作为宾语.因此有一点要注意,不及物动词由于不加宾语,没有被动形式,但不及物动词如果与某些介词构成介词短语,可以用被动.例如The fire had been put out before the fireman arrived. Put是不即物动词,但put out是及物动词
四、应用到各种时态和句型如下：
① 一般式（一般现在,一般过去,一般将来）：am, is, are, was, were, is going to be , will be+done.ie. Once environmental damage is done, it takes many years for the system to recover. 本句的意思是：“环境一旦遭到破坏,需要多年时间才能恢复过来.”do作为及物动词有“引起,产生”的含义,do damage的意思是“造成破坏”.主语damage是及物动词do的动作对象,谓语应当用被动语态.同样的,还有,I will mend the machine.相当于The machine will be mended （by me）.
② 进行时（现在进行、过去进行、将来进行）：be+being+P.P. ie.The classroom is being cleaned.
③ 完成时（现在完成、过去完成、将来完成）：have/has been + P.P.：例如The machine will have been repaired by 3 o’clock this afternoon.再如：My homework has been finished.
其他时态依词类推,可得到结果.
④情态动词的被动语态：主语 + 情态动词 + be动词 + 动词过去分词,例如Your teeth must be brushed.
⑤ 不定式的被动语态：to be done例：The no-shows have to be considered when deciding the rate of overbooking.（确定超过接待能力的预定时必须考虑预定了房间却来不了的客人.）
注意：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hear, watch, make, help, let等,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*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.
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.
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