This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nutrition and health, Subject name: Social & Preventive Medicine
[{'content': 'Double edged sword is - \nSelect and explain. \nA. Chlorine, B. Fluorine, C. Lead, D. Selenium', 'role': 'user'}, {'content': "Answer: B \nExplanation: Fluorine is often called double edged sword. Prolonged ingestion can lead to dental and Skeletal flurosis.REF. PARK'S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICAL 21ST EDITION. PAGE NO - 577", 'role': 'assistant'}]