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': 'The vitamin that is most necessary for maturation of red blood precursor cells is: \nSelect and explain. \nA. Folic acid., B. Cyanocobalamine, C. B6., D. B1.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Cyanocobalamine, folic acid, pyridoxine are essential for haematopoiesis, while cyanocobalamine is the most necessary one.', 'role': 'assistant'}]