ANS:A - shear stress is maximum.

At the point of boundary layer separation in fluid flow, the shear stress is zero. Boundary layer separation occurs when the fluid flow reverses its direction near a solid surface, causing the boundary layer to detach from the surface. At the point of separation, the velocity gradient becomes very steep, and the fluid particles lose contact with the surface, resulting in zero shear stress. This detachment creates recirculation zones and turbulence downstream of the separation point.