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': 'Optimum age for performing dacryocystorhinostomy operation in a child with congenital dacryocystitis is: \nSelect and explain. \nA. 2 years, B. 4 years, C. 6 years, D. 8 years', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. 4 years', 'role': 'assistant'}]