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 most common cause of subarachnoid hemorrhage is: \nSelect and explain. \nA. Aeriovenous malformation, B. Cavernous angioma, C. Aneurysm, D. Aneurysm', 'role': 'user'}, {'content': "Answer: C \nExplanation: Answer is C (Aneurysm): The most common cause of subarachnoid haemorrhage is rupture of a saccular aneurysm (Saccular aneurysms are synonymous with Berry Aneurysms or 'Circle of Willi's aneurysms' and most commonly occur in the anterior circulation on the Circle of Willis).", 'role': 'assistant'}]