Concept:Viscosity is the internal resistance to flow between adjacent layers of a fluid.Explanation:Viscosity depends on the nature of the fluid and is affected by temperature and pressure.Relative motion between the layers of the fluid brings viscosity into action, and the contact area affects the viscous drag between the layers.A normal reaction is a perpendicular contact force, which is not involved in the internal friction between fluid layers.Therefore, normal reaction in the fluid is not a factor that viscosity depends on.Answer:D. normal reaction in the fluid