省略to的不定式结构做宾补make/ see/ hear/watch sb. do等变成被动语态时，需要把to还原出来，变成sb. be made/ be seen/ be heard/ be watched to do.
His workers were made to work for twelve hours a day.（make sb. do在被动语态中变为sb. be made to do）
语态有两种：主动语态和被动语态。如果主语是动作的执行者，或者是说动作是由主语完成的，要用主动语态，如：We speak Chinese in China.在中国我们说汉语。
如果主语是动作的承受者，或者是说动作不是由主语而是由其他人完成的，则用被动语态，如：Chinese is spoken by us in China.在中国汉语被我们说。
扩展资料
被动语态应注意问题：
1、不及物动词无被动语态。
What will happen in 100 years./The dinosaurs disappeared about65 million years ago.
2、有些动词用主动形式表示被动意义。
This pen writes well. /This new book sells well.
3、感官动词或使役动词使用省略to的动词不定式，主动语态中不带to，但变为被动语态时，须加上to.
①makesomebody do something→somebody+ be +made to do something
②seesomebody do something→somebody +be +seen to do something
③Theboss made the little boy do heavy work.→The little boy was made to doheavy work by the boss.
4、如果是接双宾语的动词改为被动语态时，直接宾语（物）作主语，那么动词后要用介词，这个介词是由与其搭配的动词决定。
①Hegave me a book.→A book was given to me by him.
②Heshowed me a ticket.→A ticket was shown to me by him.
5、一些动词短语用于被动语态时，动词短语应当看作一个整体，而不能丢掉其中的介词或副词。
We can't laugh at him. →He can't be laughed at by us.
举例说明如下：
主动语态：
His father made him repair the
bike.
他父亲让他修理自行车。
句子分析：
his father 主语，made 谓语，him 宾语，repair the bike 不带to 的不定式短语作宾补。句中made是使让动词，所以作宾补的不定式不带to。变为被动语态要加上to。
被动语态：
He was made to repair the bike
by his father.