例句：
Diamonds are the hardest known mineral.
钻石是已知的最坚硬的矿石。
It must be stated that this illness is one of the most complex conditions known to man.
必须声明，这种疾病是人类已知的最为复杂的疾病之一。
She is best known for her work on the human brain.
她在对人脑的'研究方面最为知名。
Had I known that I would never have come.
要是早知道，我绝不会来的。
I haven't known him as long as you.
我认识他的时间没有你长。