The correct answer is: C. Polarisation
Polarization is a property of transverse waves that allows them to be aligned in a particular direction. This can be demonstrated by passing light through a polarizing filter, which will only allow light waves that are aligned in a certain direction to pass through.
Interference is the phenomenon that occurs when two waves meet and combine to form a new wave. This can be observed when two light waves are shone through two slits and the resulting pattern of light and dark bands is observed on a screen.
Diffraction is the bending of waves as they pass through a narrow opening or around an obstacle. This can be observed when light passes through a narrow slit and the resulting pattern of light and dark bands is observed on a screen.
Refraction is the bending of light as it passes from one medium to another. This can be observed when light passes from air to water and the resulting change in the direction of the light beam is observed.
Of the four options, only polarization is a property that is unique to transverse waves. Therefore, it is the only option that can be used to conclude that light is a transverse wave.