I' m sorry to keep you waitting for a long time.这句话为什么用wait的进行时?

I'm sorry to keep.为什么keep前面加to I'm sorry to keep you_______(wait)so long I'm sorry to have to inform you that y i'm sorry to keep you ----（wait） for a long time I'm sorry to keep you_______(wait) for em for a long time. I'm sorry to keep you waiting.如何划分句子成份? I'm sorry to keep you waiting.对不起,让你久等了是现在完成时? I'm sorry to have kept you waiting so long 和i' m sorry to keep you waiting so long 有啥区别 I`m sorry to hear “I'm sorry to hear I'm feel sorry to I`m sorry ___ you ___ so long.A keeping waiting B to keep waitingC keeping to wait D to keep to wait Sorry to keep you I'm so sorry!I think you must need to know that every thing is changeable.Nothing can keep still. .I'm sorry to keep you ___ for a long time.A.to wait B.waiting C.wait D.waited I'm sorry to keep you （）for a long time.I'm sorry to keep you （）for a long time.a to wait b waiting c waitd waited I’m sorry to keep you _(wait) for a long time 适当形式为什么填waiting I' m sorry to keep you waitting for a long time.这句话为什么用wait的进行时?