%_The angle subtended by the surface of sewer water with partial flow, at sewer centre is 120¬¨‚àû, the depth of sewerage is_%

%_The angle subtended by the surface of sewer water with partial flow,

1.	%_The angle subtended by the surface of sewer water with partial flow, at sewer centre is 120¬¨‚àû, the depth of sewerage is_%
A.	20 cm
B.	25 cm
C.	40 cm
D.	50 cm
Answer» E.