This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2018, Subject name: Ophthalmology
As per WHO classification of xerophthalmia, X2 is: 
Select and explain. 
A. Night blindness, B. Conjunctival xerosis, C. Bitot's spots, D. Corneal xerosis
D: Corneal xerosis
Answer: D: Corneal xerosis 
Explanation: X2 : corneal xerosis World Health Organization Re- Classification of Xerophthalmia Signs Classification Ocular Signs XN Night blindness X1A Conjunctival xerosis X1b Bitot's spots X2 Corneal xerosis X3A Corneal ulceration - Keratomalacia involving one- third or less of the cornea X3B Corneal ulceration -keratomalacia involving one-half or more of the cornea XS Corneal scar XF Xerophthalmic fundus