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': 'Pressure of oesophagus is __________ mm below ambient \nSelect and explain. \nA. 3, B. 5, C. 12, D. 18', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]