Final answer:
Lead is the most radiopaque material and has the highest rate of X-ray absorption due to its high density and electron density.
Step-by-step explanation:
The most radiopaque material and therefore the one that has the highest rate of absorption of X-rays is A. Lead.
Lead is a particularly effective shield compared to other materials, such as plastic or air, due to its high density and electron density. X-rays are ionizing radiation that interacts best with charged particles, and lead's high density of electrons allows for the efficient absorption of X-ray energy through collisions with electrons.
For example, a lead apron is commonly used in dental offices to shield the body from X-rays during dental imaging procedures.