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': 'Requirement of vitamin B12 per day for adults is: \nSelect and explain. \nA. 1 mcg, B. 3 mcg, C. 5 mcg, D. 7 mcg', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Requirement of vitamin B12 per day Healthy adults 1 mcg Pregnancy 1.2 mcg Lactation 1.5 mcg children 0.2 mcg Ref: Park 22nd edition, page 575.', 'role': 'assistant'}]