It's missing topics from A&P i.e. bones, eyes. Use Qvault for missing topics. If you're having trouble with understanding topics (i.e. learning evolution for the first time) read AP Barron's(To me the wording was more easier to follow).
Don't read Campbell's Bio for its entirety. Use it as a visual aid. I found the diagrams and images to be quite helpful.
I had questions that required prior knowledge of A&P, pretty detailed actually. I would use datqvault and destroyer to find weak areas and make sure you understand them.