This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose, Subject name: Anatomy
Which valve is present at opening of nasolacrimal duct- 
Select and explain. 
A. Hasner's valve, B. Heister valve, C. Spiral valve, D. None
A: Hasner's valve
Answer: A: Hasner's valve 
Explanation: Ans. is 'a' i.e., Hasner's valve o Nasolacrimal duct opens into inferior meatus and is closed by a mucosal flap called Hasner's valve,o Heister valve (spiral valve) is present in cyclic duct.