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
Nalgonda technique involves addition of following chemicals: 
Select and explain. 
A. Lime, bleaching powder, filter alum, B. Magnesia, calcium phosphate, filter alum, C. Alumina, carbon, lime, D. Sulphonated saw dust, coal, calcium phosphate
A: Lime, bleaching powder, filter alum
Answer: A: Lime, bleaching powder, filter alum 
Explanation: None