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': 'all are true about s1 except \nSelect and explain. \nA. lower frequency than s2, B. caused by closure of mitral valve, C. heard at the end of ventricular systole, D. better heard with diaphragm of stethescope', 'role': 'user'}, {'content': 'Answer: C \nExplanation: CHARACTERISTICS OF S1 Normally heard as fused single hea sound Medium to High Frequency Low Pitched Best heard with diaphragm M1 louder than T1 M1 best heard at apex T1 best heard at Left LSB Splitting can be heard in Expiration and L-LSB ref : harrisons 21st ed', 'role': 'assistant'}]