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: Social & Preventive Medicine
[{'content': "Bitot's spot prevalence as public health problem – \nSelect and explain. \nA. > 1%, B. > 2%, C. > 0.5%, D. None", 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]