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: Medicine
[{'content': 'The common cause of subarachnoid hemorrhage is- \nSelect and explain. \nA. Arterio-venous malformation, B. Cavernous angioma, C. Aneurysm, D. Hypertension', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]