In X-Ray Crystallography

In x-ray crystallography

A) x-ray density maps are used to calculate structure.
B) diffraction patterns are generated from crystal structure of molecules.
C) x-ray is used because of its short wavelength.
D) x-ray density maps are used to calculate structure and diffraction patterns are generated from crystal structure of molecules only.
E) x-ray density maps are used to calculate structure,diffraction patterns are generated from a crystal structure of a molecule and x-ray is used because of its short wavelength.