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': 'Endotracheal tube level is – \nSelect and explain. \nA. 5 cms above xiphisternum, B. 4 cms above carnia, C. 1 cm above carnia, D. At carnia', 'role': 'user'}, {'content': 'Answer: B \nExplanation: "Ideally, the tube tip should be 5 ±2 cm from the carina when the head and neck are in neutral position".\n___ Fundamental of anaesthesia\n\nNeck flexion causes a 2 cm descent of endotracheal tube towards carina, and neck extension causes a 2cm ascent of trachial tube tip from the carina. Therefore correct position of tip of the tube is\xa0:-\n\n5 ±2\xa0cm from carina → When neck is neutral\n3 ±2\xa0cm from carina → When neck is flexed\n7 ±2\xa0cm from carina → When neck is extended', 'role': 'assistant'}]