问题描述：
mustn't 和can't的区别 填空
Is Kate knocking at the door?No,it ( ) be Kate .She is in Shanghai now.A.can't B.must't C.shouldn't D.needn't （答案上选A,但我觉得是B,请说明原因!）
Is Kate knocking at the door?No,it ( ) be Kate .She is in Shanghai now.A.can't B.must't C.shouldn't D.needn't （答案上选A,但我觉得是B,请说明原因!）
问题解答：
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