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': 'M.C site of CA oesophagus is - \nSelect and explain. \nA. Middle 1/3rd, B. Upper l/3rd, C. Lower l/3rd, D. Lower end of esophagus', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Middle l/3rd", 'role': 'assistant'}]