![](https://cos-cdn.shuashuati.com/pipixue-web/2020-1231-2005-12/ti_inject-812ce.png)
which one of the following descriptions about the shear force in laminar flow for a round tube is correct?
A.
the shear force is a constant
B.
the shear force on pipe wall is zero
C.
the distribution of shear force over the cross section of pipe is parabola parabolic
D.
the shear force at the axis of pipe is zero and has linear relation to the radius