Complete question:
Question: Semilunar valves function to prevent blood from flowing back into the
A. ventricles during ventricular systole
B. atria during atrial diastole
C. atria during atrial systole
D. ventricles during ventricular diastole
Answer:
D. ventricles during ventricular diastole
Step-by-step explanation:
The pulmonary semilunar valve is the one through which blood flows from the right ventricle into the pulmonary trunk. Through aortic semilunar valve, blood from the left ventricle goes into the aorta. Ventricular systole opens the semilunar valves. During ventricular diastole, the blood in the pulmonary trunk and aorta close the respective semilunar valve so that blood does not backflow in the corresponding ventricles.