This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Medicine
[{'content': 'Which of the following statement is true regarding opening snap? \nSelect and explain. \nA. It is a high-pitched diastolic sound, B. It is due to opening of stenosed aoic valve, C. It indicates pulmonary aerial hypeension, D. It precedes the aoic component of second hea sound', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The high-pitched opening snap (OS) of MS occurs after a very sho interval after the second hea sound. The A2-OS interval is inversely propoional to the height of the left atrial-left ventricular diastolic pressure gradient. The intensity of both S1 and the OS of MS decreases with progressive calcification and rigidity of the anterior mitral leaflets.Ref: Harrison; 19th edition; Page no: 1447', 'role': 'assistant'}]