Steady flow:
Steady flow refers to a flow condition in which the flow pattern and velocity at any given point in a channel do not change with time. In other words, the flow remains constant at all points in the channel over a period of time.

Explanation:
To understand why the correct answer is option 'A' (steady flow), let's take a closer look at the other options and their characteristics:

Uniform flow:
Uniform flow refers to a flow condition in which the flow depth and velocity are constant at any given cross-section of a channel, but it does not necessarily mean that the flow remains constant with time. Therefore, this option does not accurately describe the flow characteristic mentioned in the question.

Laminar flow:
Laminar flow refers to a flow condition in which the fluid particles move in smooth, parallel layers with little to no mixing between them. This flow type is characterized by low velocities and a well-defined flow pattern. However, laminar flow can change with time, so it is not the correct answer in this case.

Turbulent flow:
Turbulent flow refers to a flow condition in which the fluid particles move in an irregular and chaotic manner, with significant mixing between different layers of fluid. Turbulent flow is often characterized by high velocities and an unpredictable flow pattern. Similar to laminar flow, turbulent flow can change with time, so it is not the correct answer here.

Conclusion:
Based on the given information, where the flow characteristic of a channel does not change with time at any point, the correct answer is option 'A' - steady flow. Steady flow is the only flow condition that satisfies this requirement, as it implies a constant flow pattern and velocity at all points in the channel over a period of time.