This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oesophagus, Subject name: Surgery
[{'content': 'Most common site for squamous cell carcinoma of esophagus is \nSelect and explain. \nA. Upper 1/3, B. Middle 1/3, C. Lower 1/3, D. Upper 1/2', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Middle 1/3* Esophageal Carcinoma is of two common histological typesi) Squamous cell Ca - the MC type in world (-95% according to Sabiston)ii) Adenocarcinoma - where incidence is increasing at a rapid rate and is now the MC type in USA (Ref: Harrison, Schwartz)* Distribution of Squamous Cell Ca.# Upper 1/3 - 10%# Middle 1/3 - 60%# Lower 1/3 - 30% * Adenocarcinoma is mainly located in lower 1/3.", 'role': 'assistant'}]