Answer:

d.mollusks

Explanation:

Mollusks are the soft-bodied invertebrates with one or two shells, whereas arthropods are the invertebrates with segmented bodies, jointed legs and appendages. So, this is the key difference between mollusks and arthropods.

ANSWER

D. MOLLUSKS

Phylum Mollusca is a very diverse (85,000 species ) group of mostly marine species, with a dramatic variety of form. This phylum can be segregated into seven classes: Aplacophora, Monoplacophora, Polyplacophora, Bivalvia, Gastropoda, Cephalopoda, and Scaphopoda.