一、使役动词+宾语
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。但当使役动词为被动态时，不带to不定式转为带to不定式。
主动：Let’s go and play basketball. 让我们去打篮球吧！
The teacher made him stay there quietly. 老师让他安静地呆在那里。
Her father had her do everything. 她爸爸让她做所有事。
被动：He was made to stay there quietly. 人家让他安静地呆在那里。
She was let to tell everything. 她被迫说出一切。
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：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。
