Which one of the following statements is not correct?

In the study of flow between two fixed parallel plates, the flow is assumed two dimensional.

In flow between parallel plates, if the distance between the plates and the viscosity remains constant, then the pressure gradient is also constant provided that the flow is steady.

Velocity distribution for laminar flow between two parallel plates shows that velocity varies directly with pressure gradient.

In case of flow between parallel plates, variation of shear is linear.