In case of laminar flow of fluid through a circular pipe, the

• A. shear stress over the cross-section is proportional to the distance from the surface of the pipe.
• B. surface of velocity distribution is a paraboloid of revolution, whose volume equals half the volume of circumscribing cylinder.
• C. velocity profile varies hyperbolically and the shear stress remains constant over the cross-section.
• D. average flow occurs at a radial distance of 0.5 r from the centre of the pipe (r = pipe radius).