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': 'The area of the colon which is least visualized by barium studies - \nSelect and explain. \nA. Sigmoid, B. Hepatic flexure, C. Splenic flexure, D. Caecum', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]