This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Ocular Embryology& Anatomy, Subject name: Ophthalmology
Structure with highest refractive index 
Select and explain. 
A. Cornea, B. Lens, C. Aqueous humor, D. Vitreous humor
B: Lens
Answer: B: Lens 
Explanation: Lens - 1.41 Aqueous humor - 1.34 Cornea - 1.38 Vitreous humor - 1.34