This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S, Subject name: Medicine
Following Is true regarding opening snap - 
Select and explain. 
A. It is a high-pitched diastolic sound, B. It s due to opening of stenosed aoic valve., C. It indicates pulmonary aerial hypeension., D. It preceedes the aoic component of second hea sound,
A: It is a high-pitched diastolic sound
Answer: A: It is a high-pitched diastolic sound 
Explanation: The high pitched opening snap (OS) of MS occurs after a very sho interval after the second hea sound. The opening snap (OS) of the mitral valve is most readily audible in expiration at, or just medial to, the cardiac apex. This sound generally follows the sound of aoic valve closure (A 2 ) by 0.05-0.12 s. The time interval between A 2 and OS varies inversely with the severity of the MS. The OS is followed by a low-pitched, rumbling, diastolic murmur, heard best at the apex with the patient in the left lateral recumbent position. In general, the duration of this murmur correlates with the severity of the stenosis in patients with preserved CO. ( Harrison&;s principle of internal medicine,18th edition,pg no. 1931 )