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
Vitamin B12 and folic acid supplementation in megaloblastic anemia leads to the improvement of anemia due to : 
Select and explain. 
A. Increased DNA synthesis in bone marrow, B. Increased Hemoglobin production, C. Erythroid hyperplasia, D. Increased iron absorption
A: Increased DNA synthesis in bone marrow
Answer: A: Increased DNA synthesis in bone marrow 
Explanation: A i.e. Increased DNA synthesis in bone marrowCobalt containing Vitamin B12 is found only in food of animal origin and is absorbed from distal ileumQ. B12 & folic acid supplements treat pernicious (megaloblastic) anemia by increasing DNA synthesis in bone marrowQ.