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
Removal of bacteria is: 
Select and explain. 
A. Better with slow sand filter, B. Better with rapid sand filter, C. Equal with both, D. Depends on hardness of water
A: Better with slow sand filter
Answer: A: Better with slow sand filter 
Explanation: None