Bragg's Law for X-Ray Diffraction Is 2d Sin $\theta$ = M $\lambda$

Multiple Choice

Bragg's law for x-ray diffraction is 2d sin $\theta$ = m $\lambda$ .The quantity d is:

A) the height of a unit cell
B) the smallest interatomic distance
C) the distance from detector to sample
D) the distance between planes of atoms
E) the usual calculus symbol for a differential