Final answer:
During late ventricular relaxation, the ventricles continue passively filling with blood, the atrioventricular valves open, and the semilunar valves remain closed.
Step-by-step explanation:
During late ventricular relaxation, the ventricles continue passively filling with blood. The atrioventricular (tricuspid and mitral) valves open, allowing blood to flow from the atria into the ventricles. The semilunar (pulmonary and aortic) valves remain closed to prevent backflow into the ventricles.