Which event occurs during ventricular diastole?

The coronary aeries are branches from the right and left cusps of the aoic valve. So, during systole, when the ventricles are contracting and the aoic valve is open, cusps of the aoic valve are covering the openings to the coronary aeries. This blockage, as well as the contraction of the ventricles, prevents the coronary aeries from filling. Instead, theyfill during ventricular diastole. The mitral valve and tricuspid valve are open during diastole since the ventricles are filling with blood. The pulmonic valve and aoic valve are closed during diastole since they are not being pushed open by the force of flowing blood. Ref: Barrett K.E., Barman S.M., Boitano S., Brooks H.L. (2012). Chapter 30. The Hea as a Pump. In K.E. Barrett, S.M. Barman, S. Boitano, H.L. Brooks (Eds), Ganong's Review of Medical Physiology, 24e.