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': 'Nalgonda technique is used in \nSelect and explain. \nA. Epidemic dropsy, B. Endemic ascites, C. Endemic fluorosis, D. Chlorination of water', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]