This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Water, Subject name: Social & Preventive Medicine
[{'content': 'Nalgonda technique for defluoridation of water consists of adding in sequence? \nSelect and explain. \nA. Lime + Soda, B. Soda + Alum, C. Alum + Soda, D. Lime + Alum', 'role': 'user'}, {'content': "Answer: D \nExplanation: NALGONDA TECHNIQUE:- Developed by National environment engineering research institute (NEERI), Nagpur for Defluoridation of water. It involves 'addition of Lime, Alum, and Bleaching powder' (Mnemonic: LAB) followed by Flocculation, Sedimentation and Filtration. In Nalgonda technique, Aluminum is major de-fluoridating agent.", 'role': 'assistant'}]