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': 'Snow blindness is caused by : \nSelect and explain. \nA. Ultravoilet rays, B. Infrarads, C. Microwaves, D. Defect in mirror', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Ultra violet rays', 'role': 'assistant'}]