If the particles of a fluid attain such velocities that vary from point to point in magnitude and direction as well as from instant to instant, the flow is said to be-

Correct option is D

In turbulent flow, the fluid particles exhibit chaotic and irregular variations in velocity both spatially (from point to point) and temporally (over time). This type of flow is characterized by high velocity fluctuations and mixing.
 Uniform flow: The velocity remains constant at every point along the flow direction and does not vary with time.
 Laminar flow: The flow is smooth and orderly, with layers of fluid moving parallel without significant mixing or variation in velocity.
 Non-uniform flow: Velocity changes from point to point but does not necessarily indicate chaotic behavior.
 Turbulent flow: Correct, as it involves complex and irregular changes in velocity and direction.
Therefore, the correct answer is (d) Turbulent flow.