The correct answer is C. Photoelectric effect.
The photoelectric effect is the emission of electrons from a metal surface when light is shone on it. The energy of the light must be greater than a certain threshold value, called the work function, in order for electrons to be emitted. This suggests that light has a particle nature, since it must transfer energy to individual electrons in order to cause them to be ejected from the metal.
Diffraction, polarization, and interference are all phenomena that can be explained by the wave nature of light. Diffraction is the bending of light as it passes through a narrow opening or around an obstacle. Polarization is the property of light waves that allows them to be oriented in a particular direction. Interference is the interaction of two or more light waves that can result in either constructive or destructive interference.
While these phenomena
can be explained by the wave nature of light, they do not provide direct evidence of the particle nature of photons.