---I think Helen is at home.
---No, she be at home, for she phoned me from the airport just five minutes ago.
A. mustn't
B. needn't
C. can't
D. dared not
网友回答
A. mustn't
B. needn't
(答案→)C. can't
D. dared not
解析：句意：我想海伦应该在家里。不，她不可能在家里，因为她刚刚五分钟前还从机场给我打电话了。can’t不可能，用在否定句中表示对事情的强烈的否定推测。故选C