During ventricular systole
- A. the ventricles contract and the semilunar valves open
- B. the ventricles relax and fill with blood
- C. the semilunar valves close
- D. the atrioventricular valves open wide
Explanation
Systole means contraction: rising pressure in the ventricles closes the inlet atrioventricular valves and forces open the semilunar valves, ejecting blood into the arteries. Relaxation, diastole, is the opposite phase.