This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Vitamins and Minerals, Subject name: Biochemistry
[{'content': 'Deficiency of which of the following vitamins is associated with progressive keratinization of the cornea? \nSelect and explain. \nA. Vitamin A, B. Vitamin C, C. Niacin, D. Pyridoxine', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Vitamin A deficiency is the most impoant preventable cause of blindness. The earliest sign of deficiency is a loss of sensitivity to green light-followed by impairment to adapt to dim light-then night blindness (inability to see in the dark) More prolonged deficiency leads to xerophthalmia: keratinization of the cornea, and blindness', 'role': 'assistant'}]