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
Which of the following vitamins is necessary for
maturation of blood precursor cells: 
Select and explain. 
A. Vit-A, B. Thiamine, C. Riboflavin, D. Cyano cobalamine
D: Cyano cobalamine
Answer: D: Cyano cobalamine 
Explanation: None