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: Social & Preventive Medicine
[{'content': "First ocular sign of Vitamin A deficiency ? \nSelect and explain. \nA. Bitot's spot, B. Conjunctival xerosis, C. Night blindness, D. Keratomalacia", 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Conjunctival xerosis", 'role': 'assistant'}]