It's not just a question of what you know, it's a question of being able to impart what you know. This is one of the reasons the Graduate Council insists upon an oral examination. The exam is not a test of how many facts you can memorize about three broad areas, but how you've organized those facts and how you can use them to bolster your arguments. Intelligent, informed conjecture is acceptable in many cases. We're not trying to see how much they can memorize.
Departments vary in their requirements for the qualifying exam.
Whatever the format, the following tips from students who recently passed their exams may help. Talk to other students. Nearly every student we talked to said it was very helpful to talk to students who had recently passed their exams, especially to those students with committee members in common. Ask other students about the format of their exams. That was the key factor in knowing it is possible to pass.