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
Metabolically active layer of cornea is: 
Select and explain. 
A. Endothelium, B. Stroma, C. Descernets membrane, D. Epithelium
A: Endothelium
Answer: A: Endothelium 
Explanation: A i.e. Endothelium