英语四级语法知识，在中，单独考察的题几乎没有，但是语法知识点却贯穿整张试卷，下面是小编为大家整理的知识，希望可以为大家带来帮助，一起来学习一下吧。
　　 16.9 need "不必做"和"本不该做" didn't need to do表示： 过去不必做某事, 事实上也没做。. needn't have done表示： 过去不必做某事, 但事实上做了。 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，没有遇上John的车。) 典型例题 There was plenty of time. She ___. A. mustn't have hurried B. couldn't have hurriedC. must not hurry D. needn't have hurried 答案D。needn't have done. 意为"本不必"，即已经做了某事，而时实际上不必要。 Mustn't have done 用法不正确，对过去发生的事情进行否定性推断应为couldn't have done, "不可能已经"。 must not do 不可以(用于一般现在时)。