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': 'All of them are true about retinoblastoma except \nSelect and explain. \nA. Rb1 gene is located on 11q14, B. The commonest cause of intraocular calcification, C. Trilateral retinoblastoma is a combination of bilateral retinoblastoma with pinealoblastoma, D. The commonest tumour of the eye in children', 'role': 'user'}, {'content': "Answer: A \nExplanation: Retinoblastoma (RB) gene has been identified as 14 band on the long-arm of chromosome 13 (13q 14) and is a 'cancer suppressor' or 'antioncogenic' gene. Deletion or inactivation of this protective gene by two mutations (Knudson's two hit hypothesis) results in occurrence of retinoblastoma. Retinoblastoma is commonest tumor of eye in children while in adults it is malignant melanoma of choroid.", 'role': 'assistant'}]