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': "Which of the following is the earliest clinical sign of Vit A deficiency? \nSelect and explain. \nA. Bitot's spot, B. Corneal xerosis, C. Conjunctival xerosis, D. Keratomalacia", 'role': 'user'}, {'content': "Answer: C \nExplanation: The ocular manifestation of Vit A deficiency includes night blindness, conjunctival xerosis, Bitot's spot, corneal xerosis and keratomalacia. Extra ocular manifestation of Vit A deficiency includes follicular hyperkeratosis, anorexia and growth retardation. Ref: Park, 21st Edition, Page 568.", 'role': 'assistant'}]