Answer:
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.