1. Frederick William I, the king of Prussia, ____ never _____________ that his greatest gift to the Russian people would have such an amazing history.

could have imagined

情态动词＋ have done

I may have seen the film but I’m not sure. It must have rained last week. I should have told you earlier. You shouldn’t have cheated in exams. You needn’t have bought such a dear watch for her. It wasn’t a long way, we could have walked there.

can’t/couldn’t have done 一定没做(对过去情况的推测,语气较肯定，疑，否句中)

may(might) have done 可能做了（对过去情况的推测）

must have done一定做了(过去情况的推测，语气较肯定，肯定句中

should/ought to have done本该做而没做（对已发生事情的批评责怪

shouldn’t/oughtn’t to have done本不该做但是做了（同上）

needn’t have done本不必做但是做了（对已发生事情的批评责怪）

could have done本可能做而没能做（对已发生事情的后悔，遗憾）