ing与to do做宾补
现在分词通常在下列动词后作宾语补足语：see ,hear ,notice ,watch ,keep ,find ,get ,have ,feel
e.g.
·He heard someone knocking at the door .
·I”m sorry to have kept you waiting .
在see ,hear ,watch ,notice 等动词后不定式作宾语补足语与现在分词作宾语补足语的区别：
现在分词作宾语补足语表示动作正在进行；不定式作宾补表示动作从开始到结束的全过程.
e.g.·As I drove past the park ,I saw some people playing football .(= When I saw them ,they were in the middle of playing .)
·Last week ,I went to London and saw England play Brazil in the big football match .(= I saw the whole game .)
·I heard someone coming up the stairs .