Which characteristics will allow sound to travel through a medium the fastest?

The correct choice involves properties of the medium that influence the speed of sound propagation. Sound travels fastest in materials that are both stiff and dense. Stiffness refers to the material's ability to maintain shape when a force is applied. The greater the stiffness, the more quickly sound waves can travel through the medium.

Density also plays a crucial role. While it might seem that denser materials would impede the flow of sound due to increased mass, in reality, the speed of sound in a medium is influenced more significantly by the stiffness than by density itself. In fact, sound travels faster in denser materials if they are also stiff.

Therefore, the combination of being stiff allows sound waves to propagate quickly because the molecular structure of the material can transmit vibrations more efficiently. This principle explains why materials like metals, which are both dense and stiff, convey sound much faster than lighter, less stiff materials like rubber or air.

In contrast, soft or lightweight materials would not provide the necessary conditions for high-speed sound travel due to their inability to efficiently transmit vibrational energy. Hence, the characteristics that promote the fastest movement of sound through a medium are stiffness and density.