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: Medicine
Macrocytic anaemia is due to deficiency of: 
Select and explain. 
A. Vit B1, B. Vit B12, C. Vit B2, D. Vit B6
B: Vit B12
Answer: B: Vit B12 
Explanation: None