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': 'Which of the following subtypes of cataract is the most common cause of visual morbidity: \nSelect and explain. \nA. Senile, B. Congenital, C. Traumatic, D. Drug toxicity', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A: Senile Age-related/senile cataract is responsible for 48% of world blindness, according to the World Health Organization (WHO).', 'role': 'assistant'}]