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': 'Indications of tracheostomy are \nSelect and explain. \nA. Flail chest, B. Head injury, C. Tetanus, D. All', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A i.e. Flail chest; B i.e. Head injury; C i.e. Tetanus', 'role': 'assistant'}]