Which waves can travel only through solids?

S - waves

Explanation:

S - waves are known as secondary waves or shear waves. They only propagate through solid medium only.

S - waves are elastic seismic waves that propagates transversely moving materials perpendicularly along their direction. In the process, they cause shearing. Only solids have enough shear strength to withstand the movement of s-waves without getting altered. Liquids and gases cannot shear and would not allow s-waves to propagate through them.