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
Which is the innermost layer of corneal epithelium ? 
Select and explain. 
A. Keratinized squamous cells, B. Flattened squamous cells, C. Umbrella shaped cells, D. Columnar cells
D: Columnar cells
Answer: D: Columnar cells 
Explanation: Ans. is 'd' i.e., Columnar cells Corneal epithelium is stratified squamous non-keratinized type and becomes continuous with epithelium of bulbor conjunctiva at the limbus.It consists of 5-6 layers of cells. The deepest (basal) layer is made up of columnar cells, next 2-3 layers of wing or umbrella cells and most superficial two layers are of flattened cells.