A crystalline material is:

a. a three-dimensional array of points coinciding with atom positions.
b. when a small group of atoms when repeated form the complete material.
c. the manner in which ordered materials are spatially arranged.
d. when atoms are situated in a repeating array over large atomic distances.

d. when atoms are situated in a repeating array over large atomic distances.

Explanation:

A crystalline material -

It refers to the type of solid substance where the atoms or ions are arranged in a very orderly fashion , composing a well designed lattice , is referred to as crystalline material .

These type of substances are studied under a special subtopic known as crystallography .

Hence , from the given information of the question ,

The correct option is d.