Oh, if only he knew English!

唉，要是他懂英语该多好啊！

《新英汉大辞典》

Only he knew the truth.

只有他知道真相。

youdao

Only he knew how to solve the problem.

汉译英：只有他知道如何解决那个问题。

youdao

Poor Joshua Norton was not dangerous or violent, but he no longer knew what was real and what was only imaginary.

VOA: special.2009.12.14

As I said, in some context last time, how many Russian peasants died in the 1890s thinking, "Oh my god, if the Czar only knew that we're starving, how angry he would be with his officials."

就像我在上一讲提到的,有多少死于1890年代的俄国农民会想,"上帝啊,要是沙皇知道我们在挨饿就好了,他该对手下的官员发多大的火啊"

耶鲁公开课 - 欧洲文明课程节选

Aristotle went on to say that the justice needed to control this dark side of human nature can be found only in a well ordered society of free people who govern themselves, and the only one that he knew was the Polis of the Greeks.

亚里士多德还说过,正义需要用来,控制人性的丑恶面,只有在公民自治的秩序井然的,社会里才能找得到正义,他所知道的这样的社会就是希腊城邦

耶鲁公开课 - 古希腊历史简介课程节选

During closing arguments Thursday, Kevorkian told jurors that only he knew his true intent when he helped Youk die.

CNN: Kevorkian Case: Kevorkian found guilty

According to a court document filed by Twin Capital, the hedge fund firm purchased the computer for Simon to use at his home and only he knew the password.

FORBES: New York Hedge Fund Manager Claims His Wife Hacked His Computer And Stole Trading Secrets

He only knew he had been stabbed when police used a metal detector on him.

BBC: Jamie Hall jailed for Maidstone stabbing of Gurkha veteran