This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Retina, Subject name: Ophthalmology
[{'content': "Knudson's two stage hypothesis is for: \nSelect and explain. \nA. Glaucoma, B. Retinoblastoma, C. Optic Glioma, D. Meningioma", 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. (b) RetinoblastomaRef Kanski 7/e, p. 520Deletion or inactivation of RB gene by two mutations (Knudson's two hit hypothesis) results in occurrence of retinoblastoma.", 'role': 'assistant'}]