The correct answer is D. helical flow.
Helical flow is a type of fluid flow in which the fluid particles move in a helical path. This type of flow is often seen in streams and rivers, where the water flows in a spiral pattern due to the shape of the channel. Helical flow can also be seen in the air flow around airplanes and other objects.
Stream flow is a type of fluid flow in which the fluid particles move in a straight line. This type of flow is often seen in rivers and streams, where the water flows in a straight line due to the shape of the channel. Stream flow can also be seen in the air flow around buildings and other objects.
Laminar flow is a type of fluid flow in which the fluid particles move in parallel layers. This type of flow is often seen in very small pipes, where the fluid is able to flow smoothly without any turbulence. Laminar flow can also be seen in the air flow around very small objects.
Turbulent flow is a type of fluid flow in which the fluid particles move in a chaotic and unpredictable manner. This type of flow is often seen in large pipes, where the fluid is not able to flow smoothly due to the high velocity. Turbulent flow can also be seen in the air flow around large objects.