<prompt> Fouh hea sound is caused byClosure of AV valvesClosure of semilunar valvesRapid ventricular fillingAtrial contraction  <response>: A fouh sound can sometimes be heard immediately before the first sound when atrial pressure is high or the ventricle is stiff in conditions such as ventricular hyperophy. It is due to ventricular filling and is rarely heard in normal adults.Ref: Ganong;s Review of medical physiology 25th edition. Page: 542 