ANS:C - steady

Streaklines, streamlines, and pathlines are almost identical for steady fluid flow. In fluid dynamics:

• Streaklines: These are the paths traced by particles that are released into the flow at different times but at the same point. They represent the trajectory of particles over time.
• Streamlines: These are imaginary lines that are tangent to the velocity vector of the flow at any given instant. They show the direction a fluid element would follow at a specific point in the flow field.
• Pathlines: These are the actual paths traced by individual fluid particles as they move through the flow field. They illustrate the complete history of the motion of a fluid particle from its initial position to its current position.

In steady flow, the velocity field does not change with time at any point in the flow field. As a result, the trajectories of particles over time (streaklines), the instantaneous flow directions (streamlines), and the actual paths traced by individual particles (pathlines) are almost identical. Therefore, for steady flow, streaklines, streamlines, and pathlines appear nearly the same.