It must be John who is in the office.I'm sure it()be John.Isaw him off at the railway station just
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
选C 这里表示肯定的回答 后面说道了 I'm sure it 而且为了进一步证明 有说到Isaw him off at the railway station just twenty minutes ago.(20分钟前在火车站我看见他离开的)表示肯定的回答 用 can 他的否定形式 是...