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: Biochemistry
[{'content': 'Keratinising metaplasia of salivary glands results due to deficiency of \nSelect and explain. \nA. Vitamin A, B. Thiamine, C. Riboflavin, D. Vitamin E', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Vitamin A deficiency produces keratinizing metaplasia of the normally columnar ductal epithelium in the major and minor salivary glands.\nRef : Handbook of Experimental\xa0 Stomatology,edited by Samuel Dreizen, Barnet M. Levy.', 'role': 'assistant'}]