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could have虚拟语气
could (不能用 can) have done 表示“过去本能够做某事却未做。”注意：其否定形式 couldn't have done 没有虚拟语气的用法，couldn't have done 只能表推测，相当于 can't have done，意为：“过去不可能做了某事。”
此外，could have还可以表示对过去发生的事情的推测。
can/could have done 表推测一般用在否定句和疑问句中，表示不相信或怀疑的态度。
Can/Could he have passed the exam?他可能通过了考试吗？
I think that he couldn’t/can't have gone abroad. I saw him just now.我认为他不可能出国了。我刚才还看见他了。
2.The law was passed last year with strong backing from the Prime Minister Donald Tusk after the case of a man in his 40s convicted of repeatedly raping his daughter and fathering two children by her.
这句话的主干是：The law was passed last year。with strong backing是伴随状语。after the case of a man...是时间状语。
