This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment & Nutritional Pathology, Subject name: Pathology
Source of vitamin B12? 
Select and explain. 
A. Animal source, B. Plant source, C. Milk, D. Fruits
A: Animal source
Answer: A: Animal source 
Explanation: Ans. (a) Animal SourceRef: Harrison / 640Only source of vitamin B12 for humans is food of animal origin, e.g., meat, fish, and dairy products.Vegetables, fruits, and other foods of non-animal origin are free from cobalamin unless they are contaminated by bacteria. Cobalamin is synthesized solely by microorganisms.