I don't know why

#. I don't know why ~

왜 그런지 모르겠어.

 

I don't know why he is mad.

> Didn't you joke about his face? * 농담하지 않았니 개 얼굴에 대해서

What? No, my friend did! * 내친구가 그랬어

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I don't know why I got a F in this class.

I don't know why It's so cold here.

I don't know why they got divorced.

I don't know why they have no children.