我不知道你为什么要问这个问题。

I am not sure why you asked this question.

youdao

为什么要问这个问题呢？

Why do you ask this way?

youdao

“这不关你的事。你为什么要问这个问题？”那男人生气地说。

"It's none of your business. Why do you ask such a thing?" the man said angrily.

youdao

So you might ask well, why are we using this model if it clearly doesn't take into account quantum mechanics?

那么大家可能会问为什么我们要用这个,显然没有考虑量子力学的模型呢？

麻省理工公开课 - 化学原理课程节选

And if you talk to most Americans and you're like, "Oh, why should I put this article there?"

如果你这样问大多数美国人，“为什么要把这个冠词放在这儿？”

韩国人经常犯的失误 - SpeakingMax英语口语达人

So that happens like you're asking an American "Why is this article?"

所以你问一个美国人“为什么要用这个冠词？”

韩国人经常犯的失误 - SpeakingMax英语口语达人