感官动词有(see,watch,observe,look at,hear,listen to ,notice);
感官动词有一个重要用法：感官动词+宾语+do,在用作被动语态要补出to.例如:I heard her sing an English song just now.
She was heard to sing an English song just now.
另外,使役动词包括(have,let,make)也有这种用法.如：
I saw him go upstairs just now.
He was seen to go upstairs just now.