Question

— I phoned you yesterday morning. A girl answered, but I didn’t recognize the voice.

— Oh, it __________ my younger sister. She was in my room at that moment.

A. must have been             B. should have been 

C. could have been            D. may have been

Answer

A

【解析】

试题分析：句意：—昨天上午我给你打电话。一个女孩的回答，但我没听出谁的声音。—哦，那一定是我妹妹。她那一刻正在我的房间里。情态动词加动词的现在完成式形式，表示对过去的推测。A. must have been表示一定做了某事。用于肯定推测；B. should have been 本应该，表示应该做而没有做某事。C. could have been用于肯定句时，表示可能做了某事。更常用于否定推测；D. may have been 可能做过某事。表示可能性很小。结合语境判断，A最佳。

考点：考查情态动词表市对过去推测的用法。