The correct option is C Gastropoda
The Gastropoda is a taxonomic class within the phylum Mollusca. These are the largest group under the phylum Mollusca. The class Gastropoda include snails and slugs of all kind and all sizes. There are many thousands of species of sea snails and sea slugs as well as freshwater snails, freshwater limpets, land snails and land slugs. So, the correct answer is option C.