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': 'Commonest eye tumour is: \nSelect and explain. \nA. Melanoma, B. Retinoblastoma, C. Carcinoma of eyelid, D. Carcinoma of lacrimal sac', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Retinoblastoma', 'role': 'assistant'}]