问题

The problem is too difficult for him. He _______ solveit by himself without any help.
A:can't
B:mustn't
C:shouldn't
D:needn't
B:mustn't
C:shouldn't
D:needn't
正确答案是:
同类题型
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ou still working in that company, Mary—No, it is ten months ____ I worked there.
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