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
[{'content': 'Length of naso lacrimal duct is \nSelect and explain. \nA. 9 mm, B. 10 mm, C. 11 mm, D. 12 mm', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Nasolacrimal duct is about 12 - 18 mm long.', 'role': 'assistant'}]