Work done is the energy transferred to or from a system by means of mechanical work. It is the product of the force applied to an object and the displacement of that object in the direction of the force.

a) Constant Volume Process:
In a constant volume process, the volume of the system remains constant. This means that there is no change in the displacement of the system. Since work done is the product of force and displacement, and there is no displacement in a constant volume process, the work done is zero.

b) Free Expansion Process:
In a free expansion process, a gas expands into a vacuum without any external force or resistance. Since there is no external force acting on the system, no work is done. The gas expands freely, and there is no displacement in the direction of the force. Therefore, the work done is zero.

c) Throttling Process:
Throttling is a process in which a fluid passes through a restriction, such as a valve or an orifice. In this process, the pressure of the fluid decreases while the enthalpy remains constant. Since there is no change in volume or displacement, no work is done during throttling. The work done is zero.

d) All of the Above:
From the explanations above, we can see that in a constant volume process, free expansion process, and throttling process, the work done is zero. Therefore, the correct answer is option 'D' - all of the above.

In summary, work done is zero in a constant volume process, free expansion process, and throttling process because there is no change in displacement or volume, and no external force is acting on the system.