Freshman question

Hi, I am an upcoming freshman of uw. I am considering, well, nearly certain, to take bio 180 and chem 142. My sister suggests me to take one more course of general education. What course could go along with bio and chem? Also, what are the difficulties of bio 180 and chem 142? Lastly, well a 4 in Ap psychology does anything for my second major (children/family development)?