Which set correctly lists the three major mollusk classes?

Which set correctly lists the three major mollusk classes?

• A. Gastropods, Bivalves, and Cephalopods
• B. Gastropods, Cephalopods, and Annelids
• C. Bivalves, Echinoderms, Cephalopods
• D. Gastropods, Bivalves, and Mollusks

Answer: (A)

The main idea is that mollusks are grouped into distinct classes based on major body plans and typical features. The three most commonly listed major mollusk classes are gastropods, bivalves, and cephalopods. Gastropods include creatures like snails and slugs and usually have a single shell or none. Bivalves, such as clams, oysters, and mussels, have two hinged shells. Cephalopods, which include octopuses, squids, and cuttlefish, are highly mobile and have complex nervous systems and advanced adaptations. The other options mix in organisms from entirely different phyla—like annelids (segmented worms) and echinoderms (starfish, sea urchins)—or treat Mollusca as if it were a single class, which isn’t correct since Mollusca is the phylum containing multiple classes. So, listing gastropods, bivalves, and cephalopods correctly identifies the three major mollusk classes.

The main idea is that mollusks are grouped into distinct classes based on major body plans and typical features. The three most commonly listed major mollusk classes are gastropods, bivalves, and cephalopods. Gastropods include creatures like snails and slugs and usually have a single shell or none. Bivalves, such as clams, oysters, and mussels, have two hinged shells. Cephalopods, which include octopuses, squids, and cuttlefish, are highly mobile and have complex nervous systems and advanced adaptations. The other options mix in organisms from entirely different phyla—like annelids (segmented worms) and echinoderms (starfish, sea urchins)—or treat Mollusca as if it were a single class, which isn’t correct since Mollusca is the phylum containing multiple classes. So, listing gastropods, bivalves, and cephalopods correctly identifies the three major mollusk classes.