Final answer:
The correct answer is option a . The word 'wave' best matches with the option 'signal'.
Step-by-step explanation:
In physics, a wave can be defined as a disturbance that transfers energy through a medium. Some examples of waves include sound waves, light waves, and water waves. In the context of the given options, the word 'wave' best matches with option a) signal, as a signal can be considered as a form of wave that carries information or conveys a message.
Within the context of physics, a wave can be understood in several ways depending on its properties and how it propagates through a medium. For instance, a sound wave is characterized as a mechanical wave because it requires a medium to travel through and cannot propagate in a vacuum.