weight of water, the hydraulic mean depth of the sewer and the bed slope w is the unit of the sewer, then the tractive force exerted by flowing water, is________________________?

A. the flow is steady
B. the flow is streamline
C. size and shape of the cross section in a particular length remain constant
D. size and cross section change uniform¬ly along length
E. flow occurs at constant fate

A. force of adhesion
B. force of cohesion
C. force of friction
D. force of diffusion
E. none of die above