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
Most common site of congenital blockage in the nasolacrimal duct is: 
Select and explain. 
A. At the upper end, B. In the middle, C. At the lower end, D. Whole of the duct
C: At the lower end
Answer: C: At the lower end 
Explanation: Ans. At the lower end