我亲爱的孙女：从海轮离开纽约以来，我一直为你牵肠挂肚，我知道这是为什么。

My dear granddaughter, You've been on my mind ever since this ship left New York, and I know why.

youdao

我知道这是你干的，我只是想知道为什么。

I know you did it—I just want to know why.

《牛津词典》

现在，不要问我为什么，因为我真的不知道，但事实是，客户往往对 MBWA 反应很好，这是它成功的关键原因。

Now, don't ask me why, because I really have no idea, but the fact is that customers tend to respond really well to MBWA, which is the key reason for its success.

youdao

But I was convinced I'd hear the click-click-click-click-click which is what tells you you're in trouble.

我总会觉得很紧张，我不知道这是为什么,虽然我从来没有接触过放射元素。

麻省理工公开课 - 化学原理课程节选

The third derivative, unfortunately, was never given a name, and I don't know why.

遗憾的是三阶导数没有专门的名称,我也不知道这是为什么

耶鲁公开课 - 基础物理课程节选