ANS:A - area of surface in contact.

In laminar flow, the frictional resistance (also known as viscous drag) depends on several factors, but one factor it does not depend on is the pressure of flow. Here’s an explanation of each factor:

1. Area of surface in contact: The frictional resistance in laminar flow depends on the area of the surface in contact with the fluid. A larger contact area generally results in higher viscous drag.
2. Flow velocity: The frictional resistance is directly proportional to the flow velocity. Higher velocities lead to greater shear stresses and therefore higher viscous drag.
3. Fluid temperature: Viscosity of fluids typically changes with temperature, affecting the frictional resistance. However, in the context of laminar flow, the temperature primarily influences viscosity, which in turn affects frictional resistance.
4. Pressure of flow: The pressure of the flow does not directly affect the frictional resistance in laminar flow. While pressure influences the fluid density and may indirectly affect viscosity through temperature changes, it does not alter the frictional resistance in a straightforward manner.