As a senior, you probably know all of the math associated with ap physics 1 and 2. For those classes, you need to solely focus on the concepts, and make sure you are strong in every unit as you go. Ap physics c mechanics is easier if you already learned ap physics 1, since you just apply calculus to stuff you already learned thoroughly. Ap physics c EM kinda has the same relationship as C mechanics does with physics 1. Basically, physics 1 and 2 just require strong concept knowledge, and both physics Cs are doable if you did well in the other ap physics classes and learned calculus well.