I don't know what I've done to upset him, but if looks could kill...

我不知道做了什么惹他生气了，他那样子简直吓死人。

《牛津词典》

I don't know if I will meet him this evening.

我不知道今晚是否会见到他。

youdao

If he comes to ask me, I know how to reply to him properly.

他来问我，我自有话回答。

《新英汉大辞典》

"One soldier had been fighting in the jungles for years. And I don't know if it had affected him or not, but when the clerk handed him a tweed suit to try on he spent three hours searching through the fuzz for snipers."

VOA: special.2009.03.09

Sure, if my son would wake up and I didn't tell him, he wouldn't know that it was duplicate.

当然，如果我儿子醒来,可我还是没告诉他，他不会知道这塔是重新搭的。

耶鲁公开课 - 死亡课程节选

Oh yeah, I know Hanson, but if I didn't know him, I wouldn't know any farmers.

好吧,我知道汉森,但我不认识他,我一个农民都不认识

耶鲁公开课 - 古希腊历史简介课程节选

"I don't know if I've seen him do anything wrong, " he says.

BBC: Swing states cook up trouble for Obama

"I had just watched him cross where that bomb was, so I didn't know if he made it through and I couldn't find him, " she said.

NPR: Marathon Runner Witnesses Double Disasters

"I've seen Andy since 1996, and I don't know if I've ever seen him not have his slider, " Girardi said.

WSJ: Yankees' Pettitte struggles against Astros