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 length of a standard proctoscope is - \nSelect and explain. \nA. 4 inches, B. 6 inches, C. 8 inches, D. 3 inches', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]