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': "Christmas tree cataract is seen in: \nSelect and explain. \nA. Down's syndrome, B. Rubella, C. Myotonic dystrophy, D. Diabetes", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Myotonic dystrophy', 'role': 'assistant'}]