Propagation of sound waves in air is an example.
A) Isothermal Process.
B) Isobaric Process.
C) Adiabatic Process.
D) Isochoric Process.

Hint:One way to represent the propagation of sound is by the motion of constant pressure lines of wavefronts that move with time. Another way is to mark a point on a wavefront hypothetically and follow that point's trajectory over time. This latter approach is called ray-tracing and shows how the sound is refracted most clearly.

Complete step by step solution:
An isothermal process is a thermodynamic process in which the temperature of a system remains constant. The transfer of heat into or out of the system happens so slowly that thermal equilibrium is maintained. At a particular constant temperature, the change of a substance, object, or system is known as the Isothermal Process.
Sound is a sequence of pressure waves that propagates via compressible media, such as air or water. The waves may be reflected, refracted, or attenuated by the medium during their propagation.
The most common medium sound travels through is air. As the object is moving quickly back and forth, a series of compression and rarefaction is created in the air. These make the wave of sound that propagates through the medium. Compression is high-pressure region and the low-pressure region is rarefaction.
When a system undergoes a change such that no exchange of heat takes place between system and surroundings, then the process is known as an adiabatic process.

Hence, the correct answer is C.


Note: An adiabatic process occurs between a thermodynamic system and its surroundings without transferring heat or mass. The adiabatic process, unlike an isothermal process, only transfers energy to the surroundings as work.