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': 'Vitamin associated with one carbon transfer is: \nSelect and explain. \nA. Niacin, B. Thiamine, C. Ascorbic acid, D. Folic acid', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]