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': 'Iodized salt in iodine deficiency control programme is \nSelect and explain. \nA. Secondary prevention, B. Primary prevention, C. Tertiary prevention, D. Primordial prevention', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]