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': 'All of the following are causes of leukocoria except: \nSelect and explain. \nA. Coloboma of choroid, B. Coloboma of optic disc, C. Retinopathy of prematurity, D. Retinoblastoma', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Coloboma of optic disc', 'role': 'assistant'}]