Ⅰ.用所给词的适当形式填空或在空格处填入语法形式正确的词
1．Mary ought to_have_helped (help) her mother with the housework, but she didn't.
解析：句意：玛丽本来应该帮助她妈妈做家务的，但是她没有。ought to have done 表示“本来应该做某事(但实际上并没有做)”，具有遗憾或责备的意味。
2．—Has your father got up?
—Sorry, I'm not sure. He might_have got up. Please go and see yourself.
解析：句意：——你爸爸起床了吗？——对不起，我不确定。他可能起床了。请自己去看看吧。might have done 表示对过去发生事情的推测，可能性较小。
3．Tom could_have_gone (go) to his friend's birthday party, but he was too busy yesterday.
解析：句意：汤姆本来可以去参加他朋友的生日聚会的，但是昨天他太忙了。could have done 可以用在虚拟语气中，表示“本来可以做某事(而实际上并没有做)”。
4．Mike can't__have_found (find) his car, for he came to work by bus this morning.
解析：句意：迈克一定没有找到自己的汽车，因为今天早晨他是乘公共汽车来上班的。can't have done 是对过去发生事情的否定推测。
