Final answer:
The term 'fan shell' is another name for 'oyster,' which is a type of mollusc. Oysters are part of the bivalve group and have shells that can resemble a fan, distinguishing them from crustaceans such as crabs and shrimp.
Step-by-step explanation:
The term 'fan shell' refers to a type of mollusc. Among the options provided, (b) Oyster is the answer that best fits the description of 'fan shell.' Oysters are bivalves, a group within the mollusc phylum, and they are known for their distinctive shells, which can sometimes resemble a fan in shape. Molluscs are characterized by their soft bodies, typically protected by a hard shell made by the mantle, and many have a feeding organ called the radula. Crabs, lobsters, shrimp, and krill are all crustaceans, not molluscs, and they have an exoskeleton rather than a shell produced by a mantle.