语法——情态动词Researchfindingsshowwespendabouttwohoursdreamingeverynight,nomatterwhatwehavedoneduringtheday.横线上填may,请解释语法并翻译.为什么不能用could?

Question

语法——情态动词
Research findings show we spend about two hours dreaming every night,no matter what we ____have done during the day.
横线上填may,请解释语法并翻译.
为什么不能用 could?

Answer 1

may/might have done的意思是：可能做过某事,对发生的事的较不肯定的推测.
例如：
I haven't seen him for a long time.I am not sure what has happened to him.He might have gone abroad.
could have done有两重意思：1.本来能做,但没有做成；2.可能已经做了某事,对已发生的事情进行的较为肯定的推测.
这个句子的意思是：研究发现,不管我们白天可能做过什麽,我们每晚要做大约两个小时的梦.