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
Sturm's conoid refers to configuration of the rays refracted through: 
Select and explain. 
A. Concave spherical surface, B. Convex spherical surface, C. Toric surface, D. Irregular surface
C: Toric surface
Answer: C: Toric surface 
Explanation: Ans. Toric surface