It must be John who is in the office.I'm sure it()be John.Isaw him off at the railway station justtwenty minutes ago.A.won't B.mustn't C.can't D.needn't选哪个?为什么?
问题描述：
It must be John who is in the office.I'm sure it()be John.Isaw him off at the railway station just
twenty minutes ago.
A.won't B.mustn't C.can't D.needn't
选哪个?为什么?
答