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: Social & Preventive Medicine
What is the size of particle is rapid sand filter ? 
Select and explain. 
A. 0 .1 mm, B. 0.2, C. 0.5, D. 0.4 to 0.7 mm
D: 0.4 to 0.7 mm
Answer: D: 0.4 to 0.7 mm 
Explanation: Rapid sand filter  → 0.4 - 0.7 mm
Slow sand filter → 0.2 - 0.3