The physical origin of X-ray diffraction by crystalline materials must be that: A) the distance between atoms in a crystal is approximately the same as the wavelength of X-rays (0.01- 10 nm). B) the distance between atoms in a crystal is much greater than the wavelength of X-rays (0.01-10 nm). C) the distance between atoms in a crystal is much less than the wavelength of X-rays (0.01-10 nm). D) None of the above.