what, how, why, etc. in the world idiom informal
（用在疑问句中强调很吃惊）究竟，到底
used to emphasize your surprise when asking a question
What in the world are you doing in the cupboard? 你究竟在碗柜里干什么呢？
Who in the world could do such a thing? 到底有谁能做这样的事？