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': "'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: Deletion or inactivation of RB gene by two mutations (Knudson's two hit hypothesis) results in occurrence of retinoblastoma.", 'role': 'assistant'}]