This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nose and paranasal sinuses, Subject name: ENT
[{'content': 'The valve of Hasner is \nSelect and explain. \nA. Opening of nasolacrimal duct, B. Sphenoidal sinus opening, C. Frontal sinus opening, D. Ethmoidal sinus opening', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Nasolacrimal duct (NLD) opens into the Inferior meatus through the Hasner`s valve.The direction of NLD--downward, backward, and laterally from the lacrimal sac to the nose, Length- 1.8 cmSphenoid sinus and posterior ethmoids open into the sphenoethmoidal recess (Superior meatus)Frontal, Maxillary and Anterior ethmoids open into the middle meatus.Ref: Hazarika; 3rd ed; Pg 240', 'role': 'assistant'}]