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 the nasolacrimal duct is about: 
Select and explain. 
A. 8-12 mm, B. 22-34 mm, C. 12-18 mm, D. 18-21 mm
C: 12-18 mm
Answer: C: 12-18 mm 
Explanation: Ans. 12-18 mm