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': 'Which is the most reliable diagnostic method for staging the oesphageal cancer? \nSelect and explain. \nA. MRI, B. Endoscopic ultrasound, C. CT scan, D. Thoracoscopy', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Endoscopic ultrasound", 'role': 'assistant'}]