Graph (c) represents how pressure changes as a sound wave moves through the medium, with fluctuations occurring above and below the average pressure value.

The density variation in a sound wave is represented by the fluctuations of the curve above and below the average value of density as the wave propagates in the medium.

One can expect to learn more about transverse waves in higher classes as part of advanced physics studies.

Individual particles of the medium oscillate up and down about their mean positions as a transverse wave passes through it.

Light is considered a transverse wave, but its oscillations are not of the medium particles or their pressure or density—it is not a mechanical wave.