I didn't see her at the meeting this morning; she can't / couldn't have spoken at the meeting.
He can't have finished the work so soon.
4)“should / ought to have 过去分词”表示过去本该做某事但没做,其否定式表示过去不该做某事但做了,这种句式含有不满或责备之意,ought to的语气比should强一些。如:
You ought to / should have studied harder. 你本应该更努力学习的。(但没有)
He oughtn't to / shouldn't have done that. 他本来就不该做那件事。(可是做了)
5)“would + have + 过去分词”表示对过去的某种情况进行猜测,或本来要做某事却因某种原因未做成,通常用来说明某一情况,但不像用should或ought to那样含有责备之意。如:
I guess the poet would have been about twenty when she wrote her first poem.
Another worker wouldn't have acted like that.
2.Tens of thousands of people have taken part in a rally at the Lincoln Memorial in Washington led by a conservative talk show host, Glenn Beck, who once described President Obama as a racist who hated white people.
这句话的主干是:Tens of thousands of people have taken part in a rally。at the Lincoln Memorial in Washington是地点状语。led by a conservative talk show host是过去分词做后置定语,修饰rally。who once described President Obama as是定语从句,修饰Glenn Beck。