What is the main function of the AV valves?
A) To prevent the flow of blood from atria to ventricles during atrial systole
B) To prevent the flow of blood from atria to ventricle during the quiescent period
C) To prevent the flow of blood from ventricles to atria during ventricular ejection
D) To prevent the flow of blood from arteries back into the ventricles during isovolumetric relaxation