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': 'First line investigation for esophageal carcinoma is: March 2004 \nSelect and explain. \nA. X-ray, B. Barium meal, C. Endoscopy, D. 24 hours pH measurement', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C i.e. Endoscopy', 'role': 'assistant'}]