英语情态语气选择疑问—I stayed at a hotel while in New York.—Oh?Did you

英语情态语气选择疑问
—I stayed at a hotel while in New York.
—Oh?Did you You______with Barbara.
A.could have stayed B.could stay
C.would stay D.must have stayed
could have done在这里是什么意思,为什么不选D?
I______have been more than six years old when the accident happened.
A.shouldn’t B.couldn’t C.mustn’t D.needn’t
为什么不选C