Answer:
The answer is D opening and closing of the heart valves
Explanation:
The closure of both atrial and ventricular heart valves are responsible for normal heart sounds, it should be said that blood circulation must be laminal, without turbulence or colliding with the walls of the heart.
Normal sounds of heart are caused due to "opening and closing of heart valves".
Answer: Option D
Explanation:
The two noteworthy sounds heard in the ordinary heart sound like "lub and dub". The “lub" is the main heart sound, generally named S1, and is brought about by the closing of mitral and tricuspid valves toward the beginning of systole.
The subsequent sound,"dub" or S2, is brought about by the closing of aortic and pulmonic valves, denoting the end of the systole
