One-dimensional flow refers to a type of fluid flow that occurs in a straight line with no transverse components. In other words, the flow is confined to a single dimension, typically along a pipe or channel. This type of flow is often simplified and used as a basic assumption in fluid mechanics analysis and calculations.

Uniform Flow:
Uniform flow refers to a flow where the velocity of the fluid is constant at any given point and does not change with time. In uniform flow, the fluid particles move parallel to each other in the same direction and at the same speed. While one-dimensional flow can be uniform, it is not a defining characteristic.

Steady Uniform Flow:
Steady uniform flow is a type of flow where the velocity of the fluid remains constant at all points in space and does not change with time. This means that the flow is both uniform and does not experience any fluctuations or changes. While steady uniform flow can occur in one dimension, it is not the only possibility.

Takes Place in Straight Lines:
Fluid flow can occur in various paths, including curved paths, depending on the geometry of the system. One-dimensional flow does not necessarily imply that the flow occurs in straight lines. It simply means that the flow is confined to a single dimension, which can be straight or curved.

Involves Zero Transverse Component of Flow:
One of the defining characteristics of one-dimensional flow is that it has zero transverse components. This means that the flow is confined to a single direction and does not have any lateral or sideways motion. The fluid particles move only along the length of the pipe or channel, without any movement in the transverse direction.

Takes Place in One Dimension:
The correct answer is option 'D' because one-dimensional flow refers to flow that takes place in one dimension, without any transverse components. It does not necessarily imply that the flow is uniform, steady, or occurs in straight lines. The key characteristic of one-dimensional flow is its restriction to a single dimension, with no lateral motion.

C