Sound Speed Varies by Medium Density and Elasticity

Steps:

• Sound propagates via particle vibrations, faster in denser, more elastic media.
• Solids have tightly packed particles with strong bonds, enabling quick vibrations.
• Liquids have looser packing than solids but denser than gases, so intermediate speed.
• Gases have widely spaced particles with weak interactions, resulting in slowest speed.

Why D is correct:

• Speed of sound formula $v = \sqrt{B/\rho}$ (B = bulk modulus, ρ = density) shows solids maximize elasticity-to-density ratio for fastest speed, gases minimize it for slowest.

Why the others are wrong:

• A: Gas is slowest, not fastest.
• B: Liquid is intermediate, not fastest; gas is slowest, not intermediate.
• C: Solid is fastest, not slowest; gas is slowest, not intermediate.

Final answer: D