不定式作谓语
（2）在feel（一感）,listen to,hear（二听）,let,make,have（三让）,look at,see,watch,notice（四看）等词之后接不带to的不定式作宾语补足语,强调动作的完成过程；它们作被动句的谓语时,to要补上.如：
I heard her sing today．She sang wonderfully．今天我听见她唱歌了,她唱得非常精彩.
She was heard to sing today．今天有人听见她唱歌了.（这句heard是作表语吗?)
She is often heard to sing this song（by us）．我们经常听见她唱这首歌