Solution

Pila is a genus of large freshwater snails. They are commonly called as apple snails. These are snails with an operculum. The operculum is the opening through which the organism enters inside the shell and which can be sealed when there is certain predator nearby. They belongs to family Ampullariidae. They are placed in the phylum Mollusca. These are gastropod molluscs.
Thus, the correct answer is option B.