on earth ,on the earth 有什么区别

on earth:究竟,到底例句与用法:1.Why on earth didn't you tell me the truth?你到底为什么不跟我说实话?2.Who on earth told you that?那件事究竟是谁告诉你的?3.How on earth did you know it?你到底是怎么知道的?...