一、感官动词及使役动词(如：see，feel，hear，watch，make，bid)在主动语态中用无to不定式做宾补，改为被动语态时要加to.

　　1、The middle-aged man was seen _____ out of the house on the afternoon of the murder.

　　A. came　 　B. come

　　C. to come　　D. have come

　　(答案为C)　　

       2、We were made to study harder. 我们被要求努力学习。

　　二、有些动词后面接一个介词或副词，构成短语。变被动语态时，短语动词做及物动词用。

　　1、The children are well looked after. 这些孩子得到了很好的照顾。

　　2、The doctor has been sent for. 已经派人去请大夫了。

　　三、情态动词的被动语态

　　构成：情态动词+be+过去分词。

　　1、The work must be finished before lunch. 这项工作必须在午饭前干完。

　　2、Nothing can be seen from here. 从这儿什么也看不见。

　　四、用主动表示被动的含义

　　常用：need/require +doing sth(=to be done)(此句型主语大多为物)

　　例：My room is a mess. It needs _____.

　　A to be tidying up　 　B. tidying up

　　C. to tidy up 　 　D. tidied up

　　(答案为B)