新概念2 第69课的课文中被动语态的句子变成主动语态,主动语态的变成被动语态,

一、语态概述
英语的语态是通过动词形式的变化表现出来的.英语中有两种语态：主动语态和被动语态.
主动语态表示主语是动作的执行者.
例如：Many people speak Chinese.
谓语：speak的动作是由主语many people来执行的.
被动语态表示主语是动作的承受者,即行为动作的对象.例如：Chinese is spoken by many people.主语English是动词speak的承受者.
二、被动语态的构成
被动语态由"助动词be＋及物动词的过去分词"构成.人称、数和时态的变化是通过be的变化表现出来的.现以speak为例说明被动语态在各种时态中的构成.
一般现在时：am／is／are＋spoken
一般过去时：was／were＋spoken
一般将来时：will／shall be＋spoken
现在进行时：am／is／are being＋spoken
过去进行时：was/were being＋spoken
现在完成时：have／has been＋spoken
过去完成时：had been + spoken
三、被动语态的用法
(1)不知道或没有必要说明动作的执行者是谁.
例如：Some new computers were stolen last night.一些新电脑在昨晚被盗了.(不知道电脑是谁偷的)
This bridge was founded in 1981.这座桥竣工于1981年.
(2)强调动作的承受者,而不强调动作的执行者.
例如：The glass was broken by Mike.玻璃杯是迈克打破的.
This book was written by him.这本书是他写的.
Your homework must be finished on time.你们的家庭作业必须及时完成.
四、主动语态变被动语态的方法
(1)把主动语态的宾语变为被动语态的主语.
(2)把谓语变成被动结构(be＋过去分词) (根据被动语态句子里的主语的人称和数,以及原来主动语态句子中动词的时态来决定be的形式).
(3)把主动语态中的主语放在介词by之后作宾语,将主格改为宾格.例如：
All the people laughed at him.
He was laughed at by all people.
They make the bikes in the factory.
The bikes are made by them in the factory.
He cut down a tree.
A tree was cut down by him.
五、含有情态动词的被动语态
含有情态动词的主动句变成被动句时,由"情态动词＋be＋过去分词"构成,原来带to的情态动词变成被动语态后"to"仍要保留.
We can repair this watch in two days.
This watch can be repaired in two days.
They should do it at once.
It should be done at once.
六、特殊情况
1.He made the boy work for two hours yesterday.
The boy was made to work by him for two hours yesterday.
2.Mother never lets me watch TV .
I am never let to watch TV by mother.
3.Jack gave Peter a Christmas present just now.
(1)A Christmas present was given to Peter by Jack just now.
(2)Peter was given a Christmas present by Jack just now.