*$_If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is?

*$_If the diameter of sewer is 225 mm, the gradient required for gener

1.	*$_If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is?
A.	1 in 60
B.	1 in 100
C.	1 in 120
D.	None of these
Answer» D. None of these