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
[{'content': 'Xerophthalmia Grade X-3A - \nSelect and explain. \nA. Corneal xerosis, B. Bitot spot, C. Corneal ulcer involving less than 1/3 of corneal surface, D. Corneal ulcer involving more than 1/3 of corneal surface', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Corneal ulcer involving less than 1/3 of corneal surface o WHO classification of xerophthalmiaXN Night blindnessXIA Conjunctival xerosisXIB Bitot's spotsX2 Corneal xerosisX3A Corneal ulceration/keratomalacia affecting less than one-third corneal surfaceX3B Corneal ulceration/keratomalacia affecting more than one-third corneal surfaceXS Corneal scar due to xerophthalmiaXF Xerophthalmic fundus", 'role': 'assistant'}]