Which type of wave cannot move without a medium in which to travel?

Mechanical waves cannot move without a medium

Mechanical waves require a medium to travel through so that they can transmit energy. Some examples of mechanical waves are water waves, sound waves and the waves of a slinky or jump rope. The medium through which a mechanical wave moves through can be a fluid, solid or gas. 
In short, the answer is C.

Is there any pictures in the question? i can’t answer the question without seeing the model.