If you had known what I know you would know why.

假如你知道我所知道的一切你就会晓得这是为什么道理。

youdao

If you had known when to use, that is, can foretell the!

如果你已经知道何时使用，也就是说，可以预知的！

youdao

If you had known, you could have saved my sister instead.

早知道这样，昔时还不如救我姐呢。

youdao

It was easy to tell if somebody had an infectious disease but you might not have known that they had cancer at that time and they just died.

如果有人患有感染性疾病,那很容易判断,但在那个时候医生可能不知道,病人得的就是癌症,病人就这么死去了

耶鲁公开课 - 生物医学工程探索课程节选

If only you'd known you had another 50 years, that you weren't going to die young-- or James Dean, going to burn out fast and die young-- if only you'd realized you were going to live to the ripe old age of 97, you would have picked a different life for yourself.

如果你知道自己还剩下50年，你不会英年早逝-,或者说你不会油尽灯枯，英年早逝-,如果你知道,你可以活到97岁高龄，你就会为自己选择另一种生活。

耶鲁公开课 - 死亡课程节选

Mr. McGREGOR: If you had known Shawn or lived with Shawn, you would never know that he had this really crappy hand dealt to him.

NPR: Soldier Killed in Iraq Found Family in Army

But if you had known that the media giant would be riddled with security holes, while at the same time deliberately taking on a cavalier attitude toward user privacy would you have allowed your users access to Facebook?

FORBES: Corporate Users: Are You Rethinking Facebook?

Because if I had known you just "had to pee, " I wouldn't have worried about "zone 3, " and neither would your mother.

WSJ: Keep Your Kids Safe With AT&T