句型4

It's high/about time that somebody did (should do) (should通常不省略) …早就该……

[例句]

It's time that you went to school.= It's time that you should go to school.

It's high time that we did something to improve our environment. 该是我们为环保做些事情了。

I think it's high time that she made up her mind. 我想她该拿定主意了。

句型5

情态动词+动词不定式完成结构的用法

could have done "本来可以……"(表示过去没有实现的可能)。

might have done "本来可能……;本来应该或可以做某事"(实际没有发生;含有轻微的责备语气。

should/ought to have done "本来该做某事"(而实际未做)

should not/ought not to have done "本来不该做"(实际却做过了，含有责备语气)

needn't have done "本来不必做"(但是已经做过了)

would rather have done "当时宁愿做了某事"(实际没有做过);否定式would rather not have done表达相反意思，两者都有表示"后悔"之意。