which of the following is true concerning the systolic phase of the cardiac cycle A. all cardiac valves are open during systole B. For only a very short period of time, (just before the aortic valves opens and just before the AV valves re-open) all valves are closed during systole. C. all cardiac valves are never either closed or open during systole D. the aortic valves closes just before the AV valve closes and the pulmonary arterial valve closes just before the AV valve closes. E. none of the above is correct