The news that the Portuguese Football Team failed to win the championship in their homeland must have disappointed its fans, ________it ?A.didB.did notC.mustn'tD.hasn't
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D解析must have done sth这一用法中的must不是“必须”的意思，而是表示猜测，解释为“大概，可能”，因此反义疑问句用have做助动词。