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': "Sturm's conoid refers to configuration of the rays refracted through: \nSelect and explain. \nA. Concave spherical surface, B. Convex spherical surface, C. Toric surface, D. Irregular surface", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Toric surface', 'role': 'assistant'}]