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
[{'content': 'Mineral present in Vit B12 is: \nSelect and explain. \nA. Selenium, B. Cobalt, C. Iron, D. Calcium', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]