What best describes the motion of the medium particles in a longitudinal wave?

Question

The medium does not move.
The medium moves in all directions.
The medium vibrates as it moves in a circular path around the wave.
The medium vibrates parallel to the direction of the wave.

Answer 1

The best description of the motion of the medium particles in a longitudinal wave is:

The medium vibrates parallel to the direction of the wave.

In a longitudinal wave, such as a sound wave, the particles of the medium move back and forth in the same direction as the wave is traveling, creating regions of compression and rarefaction.