The correct answer is C. kinematic viscosity.
Kinematic viscosity is a dimensionless quantity defined as the ratio of absolute viscosity to mass density. It is a measure of how easily a fluid flows. A fluid with a high kinematic viscosity will flow more slowly than a fluid with a low kinematic viscosity.
Absolute viscosity is a measure of the resistance of a fluid to flow. It is defined as the ratio of the shear stress to the rate of strain.
Mass density is a measure of how much mass is contained in a given volume of a substance. It is defined as the mass per unit volume.
Specific viscosity is a dimensionless quantity defined as the ratio of the absolute viscosity of a fluid to the absolute viscosity of a reference fluid. It is used to compare the viscosities of different fluids.
Viscosity index is a measure of how much the viscosity of a fluid changes with temperature. It is a dimensionless number that is used to classify oils.