主动语态中不加to被动语态中要加to的情况
英文中，哪些动词后加不带to的不定式，变被动语态后却必须加to 呢？今天，我们来和这个知识点做个了断。
一、使役动词+宾语
The teacher made him stay there quietly. 老师让他安静地呆在那里。
The boss made him work 10 hours a day. 老板让他每天工作10小时。
Her father had her do everything. 她爸爸让她做所有事。
被动：He was made to work 10 hours a day. 老板让他每天工作10小时。
二、感官动词+宾语
在see, hear, observe, notice, feel, watch等感官动词接宾语的结构中，用不带to不定
主动：I could only see him go. 我只能看着他走。
Mother watched him eat his breakfast. 妈妈看着他吃完早饭。
We felt the house shake. 我们感到房子的震动。
被动：He was seen to enter the house. 有人看到他进入这个房子。 Someone was heard to open the door by us. 我们听到有人开门。
式。但是当以上动词为被动态时，不带to不定式转为带to不定式。
主动：Let’s go downstairs and have a cup of tea. 让我们到楼下去喝杯茶吧！
词为被动态时，不带to不定式转为带to不定式。
在let, make, have等使役动词接宾语的结构中，通常用不带to的不定式。但当使役动
三、have known+宾语
“have known+宾语” 后用不带to的不定式，意思是“看过、听过”，等于“have seen”或“have heard”。同样，若是被动态，也需要加to。
主动：We have never known the boy smile.我们从来不知道那个男孩会笑。 被动：That boy has never been known to smile. 没有人见过那个男孩笑。
到此，小伙伴们都懂了吗？
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