Final answer:
The statement is true; semilunar valves indeed close during ventricular diastole to prevent the backflow of blood from the arteries into the ventricles.
Step-by-step explanation:
The statement that semilunar valves close during ventricular diastole to prevent blood from flowing from the arteries into the ventricles is true. The semilunar valves, which comprise the aortic and the pulmonary valves, are designed to prevent the backflow of blood into the ventricles. During ventricular diastole, when the ventricles are relaxed, these valves close to keep blood that has been ejected into the aorta and pulmonary trunk from returning to the heart. Conversely, during ventricular systole, when the ventricles are contracting and ejecting blood into the arteries, the semilunar valves are open to allow blood to flow out of the heart, while the atrioventricular valves are closed to prevent backflow into the atria.