All of the following substances are crystalline except_____________?

D. Plastic

A crystalline substance is one that has a repeating, ordered arrangement of its atoms, molecules, or ions. This arrangement gives rise to a characteristic, repeating pattern of lattice points that can be observed under a microscope. Examples of crystalline substances include ice, diamond, and sucrose (table sugar). Plastic, on the other hand, is an amorphous substance, which means that it lacks a repeating, ordered arrangement of its atoms or molecules. This lack of order gives plastic a random, disordered structure, which can be seen as a lack of regular pattern when viewed under a microscope.