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: Social & Preventive Medicine
What is deficient in exclusively breast fed baby – 
Select and explain. 
A. Vitamin B, B. Vitamin A, C. Vitamin C, D. Proteins
A: Vitamin B
Answer: A: Vitamin B 
Explanation: Deficiency of Vitamin B12 may occur in exclusive breastfed infants of mother who is on strict vegetarian diet.