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': 'All except one affect minimum alveolar concentration \nSelect and explain. \nA. Premedication, B. Age, C. Altitude, D. Drugs', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Altitude does not affect MAC, since MAC is defined in terms of percentage of one atmosphere .', 'role': 'assistant'}]