不知道为什么，我决定今天，检讨一下。

I do not know why, I have decided today that review.

youdao

我不知道为什么今天这么反常。

I don't know why I'm not myself today.

youdao

我不知道为什么今天总觉得心情不好。

I don't know why but I'm feeling rather blue today.

youdao

我不知道为什么今天总觉得心情不好。

I don't know why but I'm feeling rather blue today.

youdao