It _ Mary who was in the room.I'm sure it _— It ___ Mary who was in the room.— I'm sure it ___.A.can't be,can't be B.must be,mustn't beC.must be,can't be D.can't be must be

It _ Mary who was in the room.I'm sure it _— It ___ Mary who was in the room.— I'm sure it ___.A.can't be,can't be B.must be,mustn't beC.must be,can't be D.can't be must be
It _ Mary who was in the room.I'm sure it _
— It ___ Mary who was in the room.
— I'm sure it ___.
A.can't be,can't be B.must be,mustn't be
C.must be,can't be D.can't be must be

It _ Mary who was in the room.I'm sure it _— It ___ Mary who was in the room.— I'm sure it ___.A.can't be,can't be B.must be,mustn't beC.must be,can't be D.can't be must be
选C吧
It ___ Mary who was in the room.
推测,用must be,不用can't be 吧