I don't know how you can say things like that.

　　真想不到你怎么會說出這種話來。

　　I know you did it ─ I just want to know why.

　　我知道這是你干的，我只是想知道為什么。

　　I don't know how she puts up with him.

　　我不明白她怎么受得了他。

　　Does he know to come here first?

　　他知道要先到這兒來嗎？

　　Had I known that I would never have come.

　　要是早知道，我絕不會來的。