The main difference between a radio wave and a sound wave is their different.

A) wavelengths.

B) frequencies.

C) amplitudes.

D) energies.

E) modes of travel.

Answer: modes of travel

Sound is a mechanical longitudinal wave, whose main characteristic is that it necessarily needs a medium to propagate; unlike electromagnetic waves (radio waves) that are transverse waves and can propagate in vacuum.

Therefore, the main difference between both waves is their different modes of travel, while sound needs a medium to travel, radio waves not.