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
The recommended size of endotracheal tube for 1 year old child is 
Select and explain. 
A. 2.5, B. 3, C. 4, D. 5
C: 4
Answer: C: 4 
Explanation: Tube diameter in mm
= Age in years/4 + 4
= 1/4 + 4
= 17/4
= 4.2