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': 'Visual analogue scale  most widely used to measure \nSelect and explain. \nA. Sleep, B. Sedation, C. Depth of anaesthesia, D. Pain intensity', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]