couldn't have done 表示什么
Jim!Did you have a good time at the party?
Yes,but I really _____ have because I had a lot of work to do.
A shouldn’t
B couldn’t
注解说是对过去发生的事情的否定猜测用couldn’t have done ,我不明.明明不是参加了吗?不是用shouldn’t have done “本不该”