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: Physiology
[{'content': 'Which of the following vitamins is necessary for\nmaturation of blood precursor cells: \nSelect and explain. \nA. Vit-A, B. Thiamine, C. Riboflavin, D. Cyano cobalamine', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]