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: Medicine
[{'content': "For comparison grading of pain the scale used is - \nSelect and explain. \nA. Face's scale, B. CHEOPES, C. Numerical charts, D. Visual scale", 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]