The X-Rays Used in Medical Imaging Travel Through Tissue Relatively

The X-rays used in medical imaging travel through tissue relatively easily but are mostly absorbed by bone. This is because

A) only neutrons can absorb X-rays and the atoms in bone have many more neutrons than those in tissue.
B) the atoms in bone are slightly radioactive and the passing X-rays cause them to undergo fission. Since the atoms in tissue are not radioactive, they cannot undergo fission.
C) solids, such as bone, are much better at absorbing X-ray photons than are liquids, such as those in tissue.
D) the atoms in bone generally have more tightly bound electrons than those in tissue and are thus able to absorb higher energy photons.