Question

take a look 12. identify which type of wave must have a medium in order to travel?

Explanation:

Mechanical waves rely on a medium (like solids, liquids, or gases) for their propagation. This is in contrast to electromagnetic waves (such as light) which can travel through a vacuum. The interaction between particles in the medium (e.g., vibration of molecules in sound waves) is what allows mechanical waves to move.

Answer:

Mechanical waves.