Sound waves travel fastest through:

steel, water, or air?

Sound waves travel fastest through steel.

Steel because it's a solid.

Yes, that's correct. The speed of sound waves is determined by the density and elasticity of the medium it travels through. Solids, such as steel, have a higher density and elasticity compared to liquids or gases, which results in the sound waves traveling faster through them.

Sound waves travel fastest through solid materials, such as steel.