To fulfill the adequate permeability the D15 of filter/D15 of foundation ratio should be greater than?

To fulfill the adequate permeability the D15 of filter/D15 of foundati

1.	To fulfill the adequate permeability the D15 of filter/D15 of foundation ratio should be greater than?
A.	5
B.	10
C.	15
D.	20
Answer» B. 10