Sound speed increases from gas to liquid to solid due to particle proximity

Steps:

• Sound propagates via particle vibrations; speed depends on how closely particles interact.
• In gases, particles are far apart with weak forces, slowing sound transmission.
• In liquids, closer particles and stronger forces increase speed over gases.
• In solids, tightly packed particles with high elasticity yield the fastest speed.

Why A is correct:

• Matches the formula $v = \sqrt{B/\rho}$, where bulk modulus $B$ rises sharply from gas to solid, outpacing density $\rho$ increases, making sound fastest in solids.

Why the others are wrong:

• B: Places gas slowest, but liquids are faster than solids.
• C: Starts with solid fastest, reversing the actual order.
• D: Correctly orders solid to liquid but wrongly puts gas faster than liquid.

Final answer: A