问题描述：
can,must
It ____ be my uncle.He has gone to beijing.
A.must B.mustn't C.can D.can't
为什么选D而不选B?
It ____ be my uncle.He has gone to beijing.
A.must B.mustn't C.can D.can't
为什么选D而不选B?
问题解答：
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