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
The best position of endotracheal tube in trachea is:- 
Select and explain. 
A. 3-4 cm above carina, B. On carina, C. Midway in trachea, D. At cricoid
A: 3-4 cm above carina
Answer: A: 3-4 cm above carina 
Explanation: 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.