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: Unknown
Vitamin B12 is essential for what aspect of blood cell reproduction; 
Select and explain. 
A. Formation of hemoglobin, B. Extrusion of the nucleus from the normoblasts, C. Formation of DNA, D. Activation of erythropoietin
C: Formation of DNA
Answer: C: Formation of DNA 
Explanation: Within 6-9 hours of treatment with vitamin B12 formation of nuclear DNA component promotes normoblastic reaction of the bone marrow, Folic acid also promotes the formation of nucleic acids .