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': "Wernicke's encephalopathy is due to the deficiency of: \nSelect and explain. \nA. Niacin, B. Cyanocobalamine, C. Pantothenic acid, D. Thiamine", 'role': 'user'}, {'content': 'Answer: D \nExplanation: D Harper, 26th ed. p. 489 & 25th ed, p. 628', 'role': 'assistant'}]