Which of the following is NOT true for ventricular systole? The ventricles contract during ventricular systole. O The atria contract during ventricular systole. O The semilunar valves open during ventricular systole. The atrioventricular valves close at the beginning of ventricular systole. O Blood flows through the aortic and pulmonary semilunar valves during ventricular systole.