This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Inhalational Anesthetic Agents, Subject name: Anaesthesia
[{'content': 'Stages of anaesthesia was described by:- \nSelect and explain. \nA. WTG Moon, B. Oliver wendel homes, C. John snow, D. Guedel', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]