The question is a question asked in the middle - end scenes of Dav Pilkey's book, Ook and Gluk the kung-fu cavemen. It is repeatedly asked by master Wong because Ook and Gluk really want the black belt. They almost always used to get it wrong, until the end of the book, when they get it right and go to save Caveland, their home town.
The question is "who is the greatest man?" and the correct answer at the end of the book is "nobody".