Heart sound 2 (choose all correct) is generated by the closing of the atrioventricular valves occurs when the aortic and pulmonary valves backfill with blood marks the beginning of isovolumic relaxation is associated with turbulence during atrial contraction

occurs when the aortic and pulmonary valves backfill with blood

The second heart sound,that is heard in normal hearts, is generated by the closing of the semilunar valves((the aortic valve and pulmonary valve). Before that, the first sound corresponds to the closing of the atrioventricular valves.