Question

when sound is created, it travels to the ear through a
compression.
medium.
rarefaction.
surface.

Explanation:

Sound is a mechanical wave. Mechanical waves require a medium (such as air, water, or solids) to travel through. Compression and rarefaction are parts of a sound wave (longitudinal wave) itself, not what the sound travels through. A surface is too vague in this context compared to the scientific term "medium" for wave - propagation.

Answer:

medium.