【正确答案】 B

【答案解析】An S3 is heard following an S2, which commonly occurs in clients experiencing heart failure and results from increased filling pressures. An S1 is a normal heart sound made by the closing of the mitral and tricuspid valves. An S4 is heard before an S1 and is caused by resistance to ventrieular filling. A murmur is heard when there's turbulent blood flow across the valves.