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: Unknown
[{'content': 'Pain rating index is presided by- \nSelect and explain. \nA. Faces scale, B. Visual analogue scale, C. Mc Gill questionnaire, D. CHEOP scale', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans-C', 'role': 'assistant'}]