I don't know why.

我不知道为什么。

I don't know why I bother! Nobody ever listens!

我不知道我干吗要浪费时间！根本没人听！

"I don't know why they left," he said dolefully.

“我不知道他们为什么离开，”他悲伤地说。

I don't know why I settled on Miami, but anyway I did.

我不知道为什么我落户到了迈阿密，但不管怎样我做了。

I don't know why everybody makes such a fuss about a few mosquitoes.

我不知道为什么所有人都为几只蚊子发这么大的牢骚。

I always end up having an argument with her, I don't know why, I just can't help it.

我总是和她意见不合，闹得不欢而散，我不知道为什么，我就是忍不住。

I don't know why the guy yelled at me. And as for going back there, certainly I would never go back, for fear of receiving further abuse.

我不知道为什么这个家伙冲我吼叫。至于回到那儿去，我肯定永远也不会回去了，生怕遭到更多的虐待。

I must—though I don't know why.

我必须这样做——尽管我不知道为什么。

I don't know why he cries.

我不知道他为什么哭。

I don't know why we haven't done more.

我不知道为什么我们没有做得更多。

I don't know why you choose Chinese class?

我不知道为什么你们选择中文课？

I don't know why we're even considering it.

我不知道我们为什么要考虑这个。

You said it. I just don't know why everyone replies this question.

你说的对，我只是不知道为什么大家都回复这个问题。

Like if people jump the traffic lights, I don't know why there isn't a camera of the traffic lights to stop people doing that.

例如，我不知道为什么不在交通灯杆上安装监控摄像机来防止人们闯红灯呢？

Like if people jump the traffic lights, I don't know why there isn't a camera at the traffic lights to stop people from doing that.

比如，为什么不在交通灯杆上安装监控摄像机来防止人们闯红灯呢？

They did hunt and they also raised cereal crops and kept sheep, but we don't know why so many of the paintings are of hunting scenes.

他们确实狩猎，也会种植粮食作物、饲养绵羊，但我们不知道为什么有这么多画与狩猎相关。

I don't know why he broke off in the middle of a sentence.

我不知道他为什么说到半中腰就停止了。

My jaw aches. I don't know why.

我下巴疼，我也不知道是怎么回事。

Drained. And you don't know why.

而你不知道这是为什么。

I don't know why I was so blunt.

我不知道自己为什么这么麻木。