Q: The arrangement ABC ABC ………. is referred to as

Explanation:
The arrangement ABC ABC is known as cubic close packing.

In crystallography, close packing refers to the way layers of atoms are stacked together to achieve the highest possible density. There are two primary types of close-packed structures: hexagonal close packing (HCP) and cubic close packing (CCP), also known as face-centered cubic (FCC) packing.

In cubic close packing, the stacking sequence follows an ABCABC pattern. This means that each new layer is positioned in the depressions of the previous two layers, creating a repeating three-layer cycle. This arrangement allows for efficient space utilization and maximizes the packing density of the atoms.

On the other hand, hexagonal close packing follows an ABAB pattern, where each layer alternates between two positions. Tetrahedral and octahedral close packing are terms that describe the types of voids created within the packed layers but are not used to describe the overall stacking sequence.

Therefore, the correct answer is cubic close packing because the ABCABC arrangement specifically characterizes this type of close-packed structure.