(5)may/might have done表示对过去发生的事情的推测，意思是"也许已经做了某事，可能已经做了某事"，多用在肯定句中，用might时表示语气更加不肯定。

You might have read about the news in the papers.

你可能已经在报上看过这个消息了。

用适当的情态动词的肯定或否定形式填空

1．I can't find my purse.I could/might have left it in the supermarket yesterday，but I'm not sure.(2018·天津)

2．My room is a mess，but I needn't clean it before I go out tonight.I can do it in the morning.(2017·天津)

3．George can't have gone too far.His coffee is still warm.(2016·浙江)

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

5．-Sorry，Mum! I failed the job interview again.

-Oh，it's too bad.You should have made full preparations.(2015·福建)

6．My book，The House of Hades，is missing.Who could have taken it？(2014·陕西)

7．Since nobody gave him any help，he must have done the research on his own.

(2013·新课标全国Ⅱ)

Ⅰ.选词填空

1．As there was no bus，we had to(had to；should) walk home.

2．I want to go to the office，but you need not go(need not to go；need not go) with me.

3．I ought to have taken(to have taken；to take) those books to the library last week.

4．The mother told her son，"You mustn't(wouldn't；mustn't) eat with your fingers！"

5．He went on foot，but he should have gone(ought have gone；should have gone) by bus.

Ⅱ.完成句子

1．你应该在家里放一个简易的急救箱以防有任何事故。

You should/ought to keep a simple first aid box at home for any accidents.

2．经理脾气太暴躁，我不敢告诉他这个坏消息。

The manager is so hot­tempered that I dare not tell him the bad news.

3．你没必要拿四个，两个就够了。

You needn't fetch four；two will do.