This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cornea, Subject name: Ophthalmology
Corneal transparency is maintained by: 
Select and explain. 
A. Bowman's membrane, B. Endothelium, C. Keratocytes, D. Descemet's membrane
B: Endothelium
Answer: B: Endothelium 
Explanation: The primary mechanism controlling stromal hydration is a function of the corneal endothelium which actively pumps out theelectrolytes and water flows out passively. Endothelium consists of a single layer of flat polygonal (mainly hexagonal) epithelial cells (misnamed as endothelium) which on slit-lamp biomicroscopy appear as a mosaic.