This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Head and neck, Subject name: Anatomy
[{'content': 'The following is true about nasolacrimal duct \nSelect and explain. \nA. Directed downward, forward, and medially, B. Directed downward, backward and laterally, C. Drains in posterior pa of inferior meatus, D. 18 cm in length', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ref BDC volume 3,6th edition pg 76 It begins at the lower end of the lacrimal sac, runs downwards, backwards and laterally, and opens into the inferior meatus of the nose. Nasolacrimal duct is a membranous passage 18mm long. Notes: A fold of mucous membrane called valve of Hasner forms an imperfect valve at the lower end of the duct.', 'role': 'assistant'}]