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': 'Minimum alveolar concentration is an indicator of \nSelect and explain. \nA. Efficacy of anaesthetic, B. Potency of anaesthetic, C. Rate of onset of action, D. None', 'role': 'user'}, {'content': 'Answer: B \nExplanation: MAC indicates potency of inhalational anaesthetic agent.', 'role': 'assistant'}]