This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Ophthalmology
[{'content': 'Circumcorneal vascularization is seen in deficiency of \nSelect and explain. \nA. Vit D, B. Vit A, C. Riboflavin, D. Thiamine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: .', 'role': 'assistant'}]