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
Length of naso lacrimal duct is: 
Select and explain. 
A. 10 mm, B. 11 mm, C. 12 mm, D. 9 mm
C: 12 mm
Answer: C: 12 mm 
Explanation: Ans. 12 mm