For the first time the W.H.O.raised its alert level from phase four to phase five on April twenty-ninth.

VOA: special.2009.05.06

O Right there, order n. So I have order n operations at each level in the tree. And then how many levels deep am I? Well, that's the divide, right? So how many levels do I have?

在这儿,所以我在树的每个层次都要做O的操作,那个这棵有多少层呢？,这是一个除法，不是吗？

麻省理工公开课 - 计算机科学及编程导论课程节选