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: Anaesthesia
[{'content': 'Pain rating index is provided by \nSelect and explain. \nA. Faces scale, B. Visual analogue scale, C. Mc Gill questionniare, D. CHEOP scale', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Mc Gill questionnaire', 'role': 'assistant'}]