Allotropy (polymorphism): definition based on crystal structure changes with temperature Identify the correct statement describing an allotropic material. Choose the correct description.

Concept
Allotropy (polymorphism in metals) is the ability of a material (e.g., iron, carbon as graphite/diamond) to exist in more than one crystal structure depending on temperature (and sometimes pressure/composition).

Eliminate options
(a) contradicts allotropy; (b) describes amorphous solids, not crystalline allotropes; (d) is incorrect because only (c) is true for allotropy.

Final Answer
Exhibits different crystal structures at different temperatures