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': '3rd constriction of the oesophagus is at the level of? \nSelect and explain. \nA. Left brunchus crossing the aoa, B. Where it pierces the diaphragm, C. Junction of the oesophagus and stomach, D. Cricopharynx', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Where it pierces the diapharm", 'role': 'assistant'}]