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
Congenital obstruction of the lacrimal drainage system usually occurs at 
Select and explain. 
A. Common canaliculus, B. Lacrimal sac, C. Valve of Hasner, D. Valve of Rosen muller
D: Valve of Rosen muller
Answer: D: Valve of Rosen muller 
Explanation: Value of Hasner is at the opening of NLd into inferior meatus.