Stream lines and path lines always coincide in case of A. steady flow B. laminar flow C. uniform flow D. turbulent flow

The correct answer is A. steady flow.

Streamlines are lines that are tangent to the velocity vector at each point. Pathlines are lines that

In laminar flow, the fluid particles move in smooth, parallel layers. The streamlines are still tangent to the velocity vector at each point, but they are not straight lines because the fluid particles are moving in different directions.

In uniform flow, the velocity vector is the same at all points in the fluid. The streamlines are therefore straight lines. However, the pathlines will not coincide with the streamlines because the fluid particles are moving in different directions.

In turbulent flow, the fluid particles move in a chaotic, unpredictable manner. The streamlines are therefore not straight lines and do not coincide with the pathlines.