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
Nalgonda technique for defluoridation of water consists of adding in sequence? 
Select and explain. 
A. Lime + Soda, B. Soda + Alum, C. Alum + Soda, D. Lime + Alum
D: Lime + Alum
Answer: D: Lime + Alum 
Explanation: 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.