Cliffs ap bio, what I have been doing is reading a chapter, let's say genetics, then I will watch chads bio videos about genetics then go back and reread genetics in cliffs. Usually by then it will stick. Another way I have been studying is after I read and watch the video about genetics I will go though the destroyer and find all the problems on genetics and see how I do. Also cliffs has quizzes at the end of each chapter. Usually I do real well on the cliff quiz but then get killed on the destroyer questions. I am ALWAYS Stuck between two answers in the destroyer so if youre having a hard time on destroyer well you're not alone. Good luck!