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
[{'content': "As per WHO classification 'X2' stage of xerophthalmia refers to: \nSelect and explain. \nA. Conjunctival xerosis, B. Bitot's spots, C. Corneal xerosis, D. Corneal ulceration", 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. Corneal xerosis', 'role': 'assistant'}]