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': 'Most common site for squamous cell ca. esophagus is \nSelect and explain. \nA. Upper third, B. Middle third, C. Lower third, D. Gastro-esophageal junction', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Middle third Distribution of Squamous cell Ca Upper 1/3 10% Middle 1/3 60% Lower 1/3 30% (Values according to Sabiston 17/e, may be different in other texts but are approx. the same)", 'role': 'assistant'}]