The correct answer is D. Phylum.
A phylum is a taxonomic rank below kingdom and above class. It is the third highest taxonomic rank in the International Code of Zoological Nomenclature (ICZN). A phylum is a group of related animals that share a common ancestor.
Molluscs are a phylum of invertebrate animals that includes snails, clams, octopuses, and squid. Molluscs are characterized by a soft body that is often protected by a hard shell. They have a muscular foot that they use for locomotion, and a radula, which is a tongue-like organ that they use for feeding.
Cuttlefish are a type of mollusk that is closely related to octopuses and squid. They have a soft body that is protected by a hard internal shell. They have eight arms and two tentacles, and they can change their color and shape to camouflage themselves.
The other options are incorrect because they are lower taxonomic ranks than phylum. Class is the fourth highest taxonomic rank, order is the fifth highest taxonomic rank, and family is the sixth highest taxonomic rank.