This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: vitamins, Subject name: Biochemistry
[{'content': 'The following is due to deficiency of \nSelect and explain. \nA. Vitamin A, B. Vitamin B1, C. Vitamin C, D. Vitamin D', 'role': 'user'}, {'content': "Answer: A \nExplanation: Nyctalopia(Night blindness) is the earliest symptom of vitamin A deficiency Loss of sensitivity to green light(500nm) is the earliest sign of vitamin A deficiency Up to the level of Stage 2, the manifestations are reversible if treated with vitamin A supplements. However, active conjunctival xerosis and Bitot's spots begin to resolve within 2--5 days after supplementation. Most will disappear within 2 weeks, although a significant propoion of temporal lesions may persist in shrunken form and may therefore not be completely reversible. Reference: Harpers illustrated biochemistry 30th edition", 'role': 'assistant'}]