ANS:B - a long pipe at constant rate

A steady uniform flow refers to a flow in which the velocity of the fluid at any point remains constant over time. In such flow conditions, the rate of flow, velocity, and other flow parameters do not change with time or along the length of the pipe or tube. Among the options provided, the flow condition that best describes a steady uniform flow is a long pipe at constant rate. In a long pipe with constant flow conditions, the flow rate, velocity, and other flow parameters remain constant along the length of the pipe, assuming no external factors or changes in the pipe geometry. This scenario aligns with the definition of steady uniform flow.