on earth 这里是 ：究竟,到底 的意思例如Everything is all right.What on earth are you crying for?好好儿的,你哭哪门子?We felt puzzled.What on earth did they want to do?我们都感到纳闷儿,他们到底想干什么?...in the world 有没有此意有的如How in the world do you expect me to know him?你究竟怎么会想到我认识他呢？