情态动词＋have done　 　　

　　[全析考法]

　　单句语法填空/单句改错

　　1．(2018·天津高考改编)I can't find my purse. I could ________ (leave) it in the supermarket yesterday, but I'm not sure.

　　解析：have left　句意：我找不到我的钱包了。我昨天可能把它落在超市里了，但我不确定。根据句中的时间状语yesterday可知空格处是对过去发生事情的推测，需用"情态动词＋have done"。

　　2．(2013·全国卷Ⅱ改编)Since nobody gave him any help, he ________ have done the research on his own.

　　解析：must　句意：既然没有人帮助他，他一定是独自完成了这项研究。根据题干中"Since nobody gave him any help"可判断设空处表示肯定的推测。

　　3．(2013·浙江高考改编)I ________ (enjoy) myself more - it was a perfect day.

　　解析：couldn't/can't have enjoyed　句意：我玩得再开心不过了--这是完美的一天。"can't/couldn't ... more"表示最高级的意思；根据题干中的was可知设空处表示"对过去发生的事情的态度"，故答案为couldn't/can't have enjoyed。

　　4．(2015·天津高考改编)I needn't worried before I came to the new school, for my classmates here are very friendly to me.________________

　　解析：worried前加have　needn't have done表示"本没有必要做"。

　　[谨记规则]

　　1．对过去发生的事情或状态进行推测

must have done sth. "(过去)一定做了某事"；语气比较肯定；用于肯定句 may (might) have done sth. "(过去)可能/也许做了某事"；语气不确定；用于肯定句和否定句 can (could) have done sth. "本来能够/可以做某事"；用于否定句和疑问句，表示对过去发生的行为的怀疑或不确定 It must have rained last night, for the road is quite muddy.