D

Step 1: To understand which option shows the particle nature of light, we first need to define what is meant by 'particle nature'. This refers to the concept that light can be understood as composed of particles called photons.
Step 2: Now, let's analyze each option:
- Option A: Refraction - This is the bending of light as it passes from one medium to another and is primarily a wave phenomenon.
- Option B: Interference - This is a result of the superposition of waves coming from coherent sources, demonstrating wave properties.
- Option C: Polarization - This is another wave phenomenon that describes the orientation of light waves.
- Option D: Photoelectric effect - This demonstrates the particle nature of light where photons striking a metal surface can eject electrons. The experiment shows that light must have particle characteristics, as classical wave theory could not explain the observations.
Conclusion: The only option that unequivocally illustrates the particle nature of light is the photoelectric effect. Hence, the correct answer is D.