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: Dental
The Nalgonda technique consist of what sequence of compounds addition? 
Select and explain. 
A. Filter alum , lime , bleaching powder, B. Lime, filter alum, bleaching powder, C. Bleaching powder, lime, filter alum, D. Bleaching powder , lime, bleaching powder
A: Filter alum , lime , bleaching powder
Answer: A: Filter alum , lime , bleaching powder 
Explanation: - Nalgonda technique was developed at NEERI (Nagpur) in 1974 by Nawlakhe and reported by Bulusu in 1988.
- Addition sequence is Sodium aluminate (Filter alum), lime, and bleaching powder to fluoride water – followed by Filtration, Sedimentation and Flocculation.
- Also note in mixing:
a. rapid mixing - 30-60 seconds with a speed of 10-20 rpm
b. slow mixing(during flocculation) - 10-15 minutes with 2-4 rpm speed.