Explanation

The speed of sound depends strongly on the medium: it is greatest in solids (about 5,000 m/s in steel), lower in liquids (about 1,480 m/s in water) and least in gases (about 343 m/s in air at 20 deg C), because the elastic stiffness that transmits the wave increases in that order. Option (D) is the only statement matching this order. Options (B) and (C) reverse or scramble the correct sequence, and (A) wrongly claims independence of the medium.