This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Airway, Subject name: Anaesthesia
[{'content': 'The best position of endotracheal tube in trachea is:- \nSelect and explain. \nA. 3-4 cm above carina, B. On carina, C. Midway in trachea, D. At cricoid', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The proximal tip of endotracheal tube is best kept 3-4 cm above carina. If it is too deep it will become endobronchial. If it is too out then accidental extubation can happen.', 'role': 'assistant'}]