The order of increasing wavelength (and decreasing energy) of the given radiations is:
Gamma Rays > X-Rays > Visible Light > Radio waves
X-rays due to the short wavelength and higher energies have the ability to penetrate through soft tissues like the skin or get absorbed by hard tissues like the bones. Thus, when the human anatomy is exposed to X-rays, bones appear white whereas the skin/tissues appear gray.
Ans: A) X-rays are used by doctors to view skeletal structures