This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
[{'content': 'The distance of aoic constriction of the oesophagus from the upper incisor teeth \nSelect and explain. \nA. 15 cm, B. 22.5 cm, C. 27.5 cm, D. 40 cm', 'role': 'user'}, {'content': "Answer: B \nExplanation: First constriction, at the pharyngo-esophageal junction, 9 cm (6 inches) from the incisor teeth. Second constriction, where it's crossed by the arch of aoa, 22.5 cm (9 inches) from the incisor teeth. Third constriction, where it's crossed by the left principal bronchus, 27.5 cm (11 inches) from the incisor teeth. Fouh constriction, where it pierces the diaphragm, 40 cm (15 inches) from the incisor teeth. Ref - sciencedirect.com", 'role': 'assistant'}]