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': 'Earliest method of diagnosing pituitary tumour \nSelect and explain. \nA. CT scan, B. Visual field chaing, C. Visual evoked potential, D. X-ray skull', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., CT Scan", 'role': 'assistant'}]