This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaesthetic equipments, Subject name: Anaesthesia
[{'content': 'Inner diameter of adult male endotracheal tube is \nSelect and explain. \nA. 2 mm, B. 4 mm, C. 6 mm, D. 9 mm', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Internal diameter of the endotracheal tube used usually for an adult male ranges from 8.0 to 9.5 ID for an adult female ranges from 6.5 to 7.5', 'role': 'assistant'}]