<prompt> First heart sound corresponds to:Mitral valve openingMitral valve closingAortic valve closingNone of the above  <response>: The first heart sound S1 includes mitral and tricuspid valve closure. The First heart sound is associated with closure of the A-V Valves.The Second heart sound Is associated with closure of the Aortic and Pulmonary Valves.The Third heart sound occurs at the beginning of the middle third of diastole. Occasionally a weak, rumbling third heart sound is heard at the beginning of the middle third of diastole. Atrial contraction sound Fourth heart sound. Reference: : Guyton and Hall Physiology page no 283,284 