Final answer:
X-rays are the most particle-like among the given options because they have shorter wavelengths and hence more energy per photon, which gives them more pronounced particle-like properties.
Step-by-step explanation:
The part of the electromagnetic spectrum that is the most particle-like among the options provided is D. X-rays. This is because the energy and therefore the particle-like behavior of light is more pronounced at shorter wavelengths. X-rays have much shorter wavelengths compared to green light, microwaves, and infrared light. Photons of X-ray light have enough energy to penetrate soft tissues, which is indicative of their higher energy and particle-like properties.
As detailed in the electromagnetic spectrum, we can see that as the wavelength decreases, the energy per photon increases. Hence, with X-rays having a shorter wavelength than green light, microwaves, and infrared light, they carry more energy per photon, giving them a more pronounced particle-like nature.