They must have known what their father was up to.

他们一定已经知道他们的父亲在暗地里做什么。

《柯林斯英汉双解大词典》

I have known what it is like to go without food for days.

我已知道数日不吃东西是什么滋味了。

《柯林斯英汉双解大词典》

What an odd coincidence that he should have known your family.

他已认识你的家人，多么不寻常的巧合。

《柯林斯英汉双解大词典》

Researchers have known since the nineteen thirties that the actively growing tip of a plant releases a hormone called auxin.

VOA: special.2009.10.13

He seems to have known something about the modern economic theory of society long before modern economics was even developed.

而且是公开的驳斥,他似乎已知现代社会的经济原理,且是在现代经济学开始发展之前。

耶鲁公开课 - 政治哲学导论课程节选

You should have known better.

你早该知道的。

I should have 实战 - SpeakingMax英语口语达人

In truth no one would have known for sure what he suffered from and we can't know either.

NPR: Book Traces Family Suffering from Deadly Insomnia

Economists since David Hume in the 18th century have known about the smooth workings of unified currency systems.

FORBES: Dollarize Emerging Markets

But we should have known that already through our past experience with the political process.

FORBES: The Looming Failure of Obamacare, Part 3: Rent-Seeking