I don't know why! he says.

“我不知道为什么！”他说。

I don't know why he came back home.

我不知道他为什么回家。

I don't know why you were surprised.

我不知道你为什么会惊讶。

My appetite has decreased recently, and I don't know why.

我最近的食量减少了，不知道为什么。

I didn't think we were going to get 99. I don't know why, but I was pleasantly surprised.

我没想到我们会得99分。不知道为什么，我又惊又喜。

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

我不知道为什么红绿灯处没有摄像头来阻止人们这样做。

I don't know why she isn't here.

我不知道她为什么不在这里。

I don't know why I wanted to meet her so much but my heart just kept telling me to go after her.

我不知道为什么我这么想见她，但我的心一直告诉我要去追她。

I don't know why he cries .

我不知道他为什么哭。

I don't know why I screamed, lol.

我不知道自己为什么尖叫，哈哈。