Answer: The correct answer is "a region of high pressure in a medium caused by a passing wave".
Step-by-step explanation:
In longitudinal wave, the particles vibrate parallel to the direction of the propagation of the wave. For example, sound wave.
Sound wave consists of compression and rarefaction.
In compression, the density is high and the pressure is also high. Here, the particles are closest together.
In rarefaction, the density is low and the pressure is low. Here, the particles are far away from each other.
Therefore, the correct option is "a region of high pressure in a medium caused by a passing wave".