The correct answer is: C. viscosity
Viscosity is the property of a fluid that describes its resistance to deformation under an applied shear stress. It is a measure of how thick or thin a fluid is. Fluids with high viscosity are thick and slow-moving, while fluids with low viscosity are thin and fast-moving.
Surface tension is the tendency of a liquid surface to contract into the smallest possible area. It is caused by the attraction between the molecules of the liquid. Surface tension is responsible for the formation of water droplets and the ability of insects to walk on water.
Coefficient of viscosity is a measure of the resistance of a fluid to flow. It is a dimensionless number that is equal to the ratio of the shear stress to the shear rate. The shear stress is the force per unit area that is required to cause a fluid to flow. The shear rate is the rate at which the fluid is flowing.
Osmosis is the movement of water molecules across a semipermeable membrane from an area of high water concentration to an area of low water concentration. It is a passive process, meaning that it does not require energy. Osmosis is responsible for the movement of water in and out of cells.
In conclusion, the property by virtue of which a liquid opposes relative motion between its different layers is called viscosity.