A solid sample is examined by X-ray diffraction. The detector records discrete, sharp spots that remain fixed as the sample is rotated. Which classification is most consistent with these data?
a) An amorphous solid lacking long-range order.
b) A crystalline solid exhibiting long-range lattice order.
c) A liquid-crystal mesophase possessing only short-range order.
d) A randomly oriented polycrystalline powder that produces concentric diffraction rings.