ANS:E - all the above.

1. Coefficient of viscosity: The coefficient of viscosity is a general term that refers to the proportionality constant between the shearing stress and the velocity gradient in a fluid. It quantifies the resistance of a fluid to flow under an applied shearing stress. The coefficient of viscosity is denoted by various symbols, with μ being a common representation.
2. Absolute viscosity: Absolute viscosity is another term for dynamic viscosity. It is a measure of a fluid's internal resistance to flow when subjected to an applied shearing stress. Absolute viscosity is constant for a given fluid at a constant temperature and pressure.
3. Dynamic viscosity: Dynamic viscosity (μ) is a measure of a fluid's resistance to flow under an applied shearing stress. It quantifies the internal friction within the fluid as it flows. Mathematically, dynamic viscosity is defined as the ratio of shearing stress to velocity gradient: τ=μ du /dy​, where τ is the shearing stress, μ is the dynamic viscosity, and du /dy ​ is the velocity gradient.
4. Viscosity: Viscosity, in general, refers to the resistance of a fluid to flow. It is a property that determines how easily a fluid flows. Viscosity encompasses dynamic viscosity, as well as other forms of viscosity such as kinematic viscosity and cinematic viscosity. However, in many contexts, when we refer to viscosity without qualification, we usually mean dynamic viscosity.