ANS:B - tapering pipe at either decreasing or increasing flow rate.

An example of unsteady non-uniform flow is the flow of liquid under pressure through a tapering pipe at either decreasing or increasing flow rate. In this scenario, as the liquid flows through a tapering pipe, the cross-sectional area changes along the length of the pipe. This change in cross-sectional area results in changes in flow velocity according to the principle of continuity, which states that the product of velocity and cross-sectional area is constant for an incompressible fluid flowing through a pipe. If the flow rate remains constant while the pipe diameter decreases (tapering pipe at decreasing flow rate), the flow velocity must increase to maintain the continuity equation. Conversely, if the pipe diameter increases (tapering pipe at increasing flow rate), the flow velocity decreases. This variation in flow velocity along the length of the pipe makes the flow unsteady (changing with time) and non-uniform (varying spatially). Therefore, the flow of liquid through a tapering pipe at either decreasing or increasing flow rate is an example of unsteady non-uniform flow.