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': 'The most common type of refractive error is: \nSelect and explain. \nA. Hypermetropia, B. Myopia, C. Astigmatism, D. None of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Astigmatism', 'role': 'assistant'}]