Final answer:
The event that occurs when the aortic valve is open is the ventricular ejection phase, where blood is pushed out of the ventricles into the pulmonary trunk and aorta.
Step-by-step explanation:
The event that occurs when the aortic valve is open is the ventricular ejection phase. During this phase, pressure in the ventricles rises above the pressure in the atria, and blood is pushed out of the ventricles into the pulmonary trunk and aorta. This is when the two semilunar valves open to allow blood flow.