Answer: The correct answer is "vibrate".
Explanation:
In longitudinal wave, the particles travel parallel to the direction of the motion of the wave.
For example, sound wave. It needs medium for their propagation. It can travel in solid, liquid and gas.
Sound wave consists of compression and rarefaction. Compression is the region where the density of the particle is more. Here, the pressure is high. Rarefaction is the region where the density of the particle is less. Here, the pressure is low.
The vibrating body causes the medium around it to vibrate. This leads to the formation of the sound waves.
Therefore, sound waves are created when something is caused to vibrate.
