ANS:E - all the above.

The Chezy's constant C in the formula V=Crs​ (where V is the velocity, r is the hydraulic radius, and s is the slope of the energy grade line) depends upon all the above factors:

1. Size of the sewer: The size of the sewer influences the flow characteristics, such as the flow depth and capacity, which in turn affect the velocity.
2. Shape of the sewer: The shape of the sewer determines the hydraulic characteristics, including the hydraulic radius r, which is a key parameter in determining flow velocity.
3. Roughness of sewer surface: The roughness of the sewer surface affects the flow resistance and friction losses, influencing the velocity and hence the value of C.
4. Hydraulic characteristics of the sewer: The hydraulic characteristics, which encompass factors such as size, shape, and roughness, collectively determine the flow behavior and performance of the sewer system.