mastn't的意思---Listen!IsthatKateplayingthepianointheroom?--No.ItbeKate.ShehasgonetoLondonA.maynotB.needn'tC.must'sD.can't

Question

mastn't的意思
---Listen!Is that Kate playing the piano in the room?
--No.It____ be Kate .She has gone to London
A.may not B.needn't C.must's D.can't

Answer 1

D 项为最好的答案.表示不可能.
A 选项的may not,表示推测,也许.而后面的She has gone to London,表明回答者已知道了kate 的去向,没有必要用推测的语气.
B 选项的needn't,need not的否定式,不是needn't,首先可以排除.
C 选项的must't,must not的否定式,就是can't,而不是must’t .