专业四级语法 | 情态动词与动词完成时连用考点归纳

1. may/might/must/can't have done 表示对过去发生事情的推测。

2. should/ought to have done 意为“本应该”，表示过去应该做某事而实际上没有做。比如：

• I ought to have known he would do a silly thing like that.

3. could have done 意为“本可以”，表示过去某事可能发生却没有发生。比如：

• I felt so regretful. I could have helped him.

4. needn't have done 意为“本不必”，表示本来没有必要做某事，但是却做了。例如：

• You needn't have finished all that—how kind of you!