This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Lens, Subject name: Ophthalmology
[{'content': 'Commonest cause of cataract- \nSelect and explain. \nA. Hereditary, B. DM, C. Trauma, D. Age related', 'role': 'user'}, {'content': "Answer: D \nExplanation: Most common type of cataract is senile (age related) cataract. Ref: Ophthalmology by Duker's 2nd/e p.420.", 'role': 'assistant'}]