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 crosssection
D. Average flow occurs at a radial distance of 0.5 r from the centre of the pipe (r = pipe radius)