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
Toughest layer of Cornea is 
Select and explain. 
A. Descement membrane, B. Endothelium, C. Connective tissue stroma, D. Pre descement membrane
D: Pre descement membrane
Answer: D: Pre descement membrane 
Explanation: Toughest layer of Cornea is Pre descement membrane.