This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': '2nd heart sound is characterized by all except \nSelect and explain. \nA. Due to closure of semilunar valves, B. Is occasionally split, C. Has longer duration than 1st heart sound, D. Marks the onset of diastole', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]