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
[{'content': "A child is exclusively fed on cow's milk, the deficiency seen in: \nSelect and explain. \nA. Iron, B. Riboflavin, C. Vitamin-A, D. Thiamine", 'role': 'user'}, {'content': 'Answer: A \nExplanation: Iron', 'role': 'assistant'}]