To determine which of the options is correct, it helps to understand the properties of longitudinal waves. Longitudinal waves are waves in which the particle displacement is parallel to the direction of wave propagation. Sound waves in air are a common example of longitudinal waves. Let's analyze each option: Option A: Have a unique wavelength Longitudinal waves, like any other type of waves, have a wavelength which is the distance between successive compressions or rarefactions. Therefore, longitudinal waves can have a unique wavelength. Option B: Have a unique wave velocity The wave velocity in a longitudinal wave is determined by the medium in which the wave is traveling. If the medium is uniform, the wave will have a unique velocity. Therefore, longitudinal waves can have a unique wave velocity. Option C: Transmit energy Waves, in general, transmit energy through the medium. This is true for both longitudinal and transverse waves. Longitudinal waves can transmit energy. Option D: Be polarized Polarization refers to the orientation of the oscillations in a wave. Only transverse waves can be polarized because their oscillations are perpendicular to the direction of wave propagation. Since the oscillations in longitudinal waves are parallel to the direction of wave propagation, they cannot be polarized. Therefore, the correct answer is: Option D: Be polarized