Question

Octopus, Squid and Cuttlefish belong to class
A. Cephalopoda
B. Apoda
C. Decapoda
D. Scaphopoda

Answer 1

Hint: Molluscs are also classified as soft-bodied, bilaterally symmetrical, segmented, coelomate animals; molluscs are typically shelled with a mantle, ventral foot, anterior head, and a visceral dorsal mass. Many of the remaining classes of molluscs demonstrate a large variation in size.

Complete answer:
The Mollusca are the largest invertebrate marine phylum. Different groups include gastropoda, bivalvia, scaphopoda, and cephalopoda.
Cephalopoda- Cephalopod, any member of the Phylum Mollusca Class Cephalopod, a small group of highly advanced and organised, solely marine animals. There are familiar representatives of octopus, squid, cuttlefish, and chambered nautilus. The extinct forms outnumber the living, with considerable variety attained by the class in late Paleozoic and Mesozoic times. With the exception of five living species of Nautilus, the extinct cephalopods are ammonites, belemnites, and nautiloids.
Apoda- An current order of amphibians, now restricted to the tropics and subtropics, adapted to a burrowing life that looks like big earthworms. They are the only living amphibians that have preserved scales in some animals, but the scales are vestigial and hidden in skin folds. They have no limbs or limb girdles, rudimentary eyes, vestigial hearing devices, a sensory sensor beneath the eye, no adult gills or gill slits, and a small or absent tail.
Decapoda- Decapod, order Decapoda, phylum Arthropoda, one of more than 8,000 species of crustaceans, including shrimp, lobsters, crayfish, hermit crabs, and crabs. The basis for the name Decapod is the presence of five pairs of thoracic legs. In size and structure, members of the order exhibit great diversity.
Scaphopoda- Because their shells are conical and slightly curved to the dorsal side, the Scaphopoda are a distinctive group of molluscs commonly known as the "tusk shells," making the shells look like small tusks. The scientific name Scaphopoda means "shovel foot," a term which refers to the animal's "head," which lacks eyes and is used in marine mud and sediments for burrowing. The most distinctive feature of cephalopods is that, as in most molluscs, the tubular shell is open at both ends, not just one end.

Hence, the correct answer is (A).

Note:
In many subgroups, typical mollusc characteristics have been significantly altered, or even lost. The giant squids, the largest living invertebrates, reach a body length of eight metres among the cephalopods, with the tentacle arms extended, the total length reaching 22 metres. Other cephalopods exceed one metre in length.