This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cataract, Subject name: Ophthalmology
[{'content': "Not a cause of pre-senile cataract: \nSelect and explain. \nA. Diabetes mellitus, B. Myotonic dystrophy, C. Posterior polar cataract, D. Marfan's syndrome", 'role': 'user'}, {'content': "Answer: D \nExplanation: Marfan's syndrome is not a cause of pre-senile cataract. Pre-senile cataract Cataract onset before 50 years of age. Causes Diabetes Mellitus. Atopic dermatitis. Steroid Induced cataract. Posterior polar cataract. Myotonic dystrophy.", 'role': 'assistant'}]