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: ENT
[{'content': 'Narrowest pa of airway is: \nSelect and explain. \nA. Subglottis, B. Carina, C. At vocal cords, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The subglottis is the narrowest poion of the airway in children, and the cricoid cailage is the only complete cailaginous ring in the airway. Because airflow in a cylinder is directly propoional to the fouh power of the radius, even a slight reduction in the area of the subglottis can lead to significant obstruction.', 'role': 'assistant'}]