This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Classification of carbohydrate, Subject name: Biochemistry
Which glycosaminoglycan is present in cornea ? 
Select and explain. 
A. Dermatan sulfate, B. Chondroitin Sulfate, C. Hyaluronic acid, D. Keratan Sulfate
D: Keratan Sulfate
Answer: D: Keratan Sulfate 
Explanation: option d : Keratan sulafte Glycosaminoglycan in cornea: Keratan sulafte (KS) >>> Chondroitin sulfate (CS) & Dermatan sulfate (DS) All are present in cornea but KS is in maximum amount Immunohistochemistry revealed the presence of both high- and low-sulphated epitopes of KS, as well as DS, throughout the cornea CS only in the peripheral cornea before the limbus. Keratan sulfate is also responsible for corneal transparency. Keratan Sulfate-I is present in cornea while Keratan Sulfate-II is present in cailages.