The correct answer is D. Light waves.
Polarization is the property of a transverse wave that specifies the orientation of its oscillations. A transverse wave is a wave in which the direction of the oscillation is perpendicular to the direction of the wave’s travel. Light is an example of a transverse wave.
Sound waves in air and longitudinal waves on a string are both longitudinal waves. In a longitudinal wave, the direction of the oscillation is parallel to the direction of the wave’s travel. Longitudinal waves cannot be polarized because the direction of the oscillation is always parallel to the direction of the wave’s travel.
Therefore, the only wave that can be polarized is light.