Asound wave is made of a series of compressions and
a.
extensions.
c.
rarefactions.
b.
volumes.
d.
refractions.

Answer;

C.  Rarefactions.

Explanation;A wave is a transmission of a disturbance from one point to another. Wave involves transmission of energy from one point to another through a materials medium.Waves may require or may nor require a material medium for transmission. Those wave that do not require material medium for transmission are electromagnetic waves while those that require material medium are called mechanical waves.Mechanical waves transfers energy through the vibration of particles of the medium through which the wave travels, while electromagnetic waves transfer energy through the vibration of electric or magnetic fields.Sound waves are examples of mechanical waves whose motion is that of a longitudinal waves. Such that there is a series of compressions and rarefactions

Sound waves consist of compressions and rarefactions.

B. a circuit. i think