I don't know what you're on about.
我不懂你在談什么。
Well, what do you know? Look who's here!
唷，真想不到！你看誰(shuí)來(lái)啦！
She of all people should know the answer to that.
在所有的人中，唯有她最應(yīng)知道那個(gè)問(wèn)題的答案。
I don't know how you can say things like that.
真想不到你怎么會(huì)說(shuō)出這種話(huà)來(lái)。
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。