Mollusks are invertebrates. What does it mean when an animal is an invertebrate?
A. They all have shells.
B. They have a backbone.
C. They do not have a backbone.
D. They live in the ocean.

c they do not have a backbone

Explanation:

Invertebrates are animals that neither possess nor develop a vertebral column (commonly known as a backbone or spine), derived from the notochord. This includes all animals apart from the subphylum Vertebrata. Familiar examples of invertebrates include arthropods (insects, arachnids, crustaceans, and myriapods), mollusks (chitons, snail, bivalves, squids, and octopuses), annelid (earthworms and leeches), and cnidarians (hydras, jellyfishes, sea anemones, and corals).