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
The focusing system of eye is composed of several refractive structures. Which of the following has the maximum refractive index? 
Select and explain. 
A. Cornea, B. Aqueous, C. Lens, D. Vitreous
C: Lens
Answer: C: Lens 
Explanation: Refractive index: It is the ratio of sine of angle of incidence to the sine of angle of refraction. The refractive index of, Cornea: 1.37 Aqueous humour: 1.33 Crystalline lens: 1.42 Vitreous humour: 1.33 Also know: The total dioptric power of the eye is about +60 D out of which about +44 D is contributed by cornea and +16 D by the crystalline lens. Ref: Ophthalmology By A. K. Khurana, 3rd edition, Page 50.