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: Surgery
[{'content': "Feature of posterior cranial fossa is: \nSelect and explain. \nA. Battle's sign., B. Guerin sign., C. Corman's sign., D. Verill's sign.", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]