If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is

If the diameter of a sewer is 150 mm, the gradient required for gener

1.	If the diameter of a sewer is 150 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» C. 1 in 120