Water filtration rate in a rapid sand filter ranges from ______________ kilolitres/m2/hr?
A. 0.1 to 1
B. 3 to 6
C. 10 to 15
D. 15 to 20
A. 0.1 to 1
B. 3 to 6
C. 10 to 15
D. 15 to 20