a. False. The Compton effect is independent of the atomic number of the material as it only involves free electrons whose binding energy is negligible.
b. False. As photon energy increases, the rate of photoelectric absorption decreases more than the Compton effect. Hence, at high photon energies, the Compton effect still predominates.
c. True. The Compton effect predominates in low-atomic-number materials e.g. air, water and tissue.
d. False. Photoelectric absorption predominates in high-atomic-number materials, e.g. lead and contrast medium.
e. False.