This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thoracic Duct & Esophagus, Subject name: Anatomy
[{'content': '2nd constriction of esophagus is due to - \nSelect and explain. \nA. Left principal bronchus, B. Arch of arorta, C. Pharyngoesophageal junction, D. None', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Arch of arorta Esophageal constrictionsNumberDistance from incisorBony levelAnatomical landmark1st2nd3rd4th15 cm (6 inches)22-5 cm (9 inches)27-5 cm (11 inches)37 -5 -40 cm (15-16 inches)C6T4T6T10At its beginning (pharyngoesophageal junction)Crossing of aortic archCrossing of left main bronchusPiercing diaphragm (at lower esophageal sphinctor)", 'role': 'assistant'}]