初中英语练习题的难点之做还是不做

　　   初中英语练习题的考点背景：

           didn't need to do表示： 过去不必做某事, 事实上也没做。.
needn't have done表现： 从前不必做某事, 但事实上做了。（习题考试注意考虑两种时态的区别）
John went to the station with the car to meet Mary, so she didn't need to walk back home. 约翰开车去车站接玛丽，所以她不必步行回家了。
John went to the station with the car to meet Mary, so she needn't have walked back home. 约翰开车去车站接玛丽，所以她本不必步行回家了。 (Mary步行回家，不遇上John的车。)

内容来自

　　初中英语练习题训练：
There was plenty of time. She ___.
A. mustn't have hurried　 B. couldn't have hurried　　C. must not hurry　 Dneedn't have hurried
答案D。needn't have done. 意为"本不必"，即已经做了某事，而时实际上不用要。
Mustn't have done 用法不正确，对从前发生的事件进行否定性推断应为couldn't have done, "不可能已经"。 must not do 不可能（用于个别当初时）。

       相对于这种初中英语练习题的考法，一般都是纠结在主语到底是做了还是没有做。需要考生们根据具体问题具体来分析，切勿看到相似习题就匆匆选答案，那往往有陷阱。

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