The correct answer is Option A: C only.

Reflection, diffraction, interference, and polarization are all phenomena that can be explained by the wave nature of light. These phenomena are evidence that light behaves as a wave, evident through various experimental observations:

• Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. The laws of reflection can be explained by treating light as waves.
• Diffraction is the bending of light around the corners of an obstacle or aperture into the region of geometrical shadow of the obstacle. This phenomenon is observed when a wave encounters an obstacle or a slit that is comparable in size to its wavelength, which is best explained by wave theory.
• Interference occurs when two or more waves superimpose to form a resultant wave of greater, lower, or the same amplitude. This phenomenon illustrates the wave nature of light through constructive and destructive interference patterns, such as those observed in the double-slit experiment.
• Polarization is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. For light waves, this can be seen as the direction in which the electric field oscillates. Polarization can only occur with waves that have transverse components, further supporting the wave nature of light.

On the other hand, the photoelectric effect cannot be explained solely by the wave nature of light. It is the emission of electrons or other free carriers when light shines on a material. Electrons emitted in this manner can be called photoelectrons. The phenomenon is best explained by Albert Einstein's quantum theory of light, where light is considered as quanta of energy called photons. This effect demonstrates the particle aspect of light, wherein each photon has a discrete packet of energy equal to $$hf$$, where $$h$$ is Planck's constant and $$f$$ is the frequency of the light.

Thus, the photoelectric effect is the correct answer because it specifically requires the particle theory of light for its explanation, unlike reflection, diffraction, interference, and polarization, which are well-explained by the wave nature of light.