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
Narrowest pa of airway is: 
Select and explain. 
A. Subglottis, B. Carina, C. At vocal cords, D. None of the above
A: Subglottis
Answer: A: Subglottis 
Explanation: 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.