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: Ophthalmology
Diameter of head mirror in ENT is: 
Select and explain. 
A. 20 cm, B. 22 cm, C. 10 cm, D. 26 cm
C: 10 cm
Answer: C: 10 cm 
Explanation: Ans. is c i.e. 10 cm Diameter of the head mirror used in ENT is 89 mm (3and half inch).