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 corneal transparency is maintained by 
Select and explain. 
A. Keratocytes, B. Bowman's membrane, C. Descement's membrane, D. Endothelium
D: Endothelium
Answer: D: Endothelium 
Explanation: D i.e. Endothelium