Do you still remember the day when we went to the Great Wall?I can't remember it well,but____sometime last autumn?A.might it be B.could it have been C.could it be D.must it have been
问题描述：
Do you still remember the day when we went to the Great Wall?I can't remember it well,but____sometime last autumn?
A.might it be B.could it have been C.could it be D.must it have been
答
现在对你来说还有些难懂，
情态动词后要加动词原形，但是可以根据需要进行变形
如此题：could have done 表示对过去已完成的时进行推测
然后再进行疑问句序的变换成B
答
你还能记起咱们去长城的那个日子吗?我记不清了,可能是去年秋天的时候吧?
could have done sth是对过去的推测,是情态动词的一种固定用法