Water filtration rate in a slow sand filter ranges from ____________ litres/m2/hr?
A. 10 to 20
B. 100 to 200
C. 1500 to 2500
D. 4000 to 5000
A. 10 to 20
B. 100 to 200
C. 1500 to 2500
D. 4000 to 5000