Have a body plan with three main parts: a visceral mass, a mantle, and a foot.

Answer;

Molluscs

Explanation;Molluscs have a body plan with three main parts: a visceral mass, a mantle, and a foot.Mantle is a soft extension of the body wall in certain invertebrates, for example, Brachiopods and molluscs, which usually secretes a shell, thin body wall of tunicates.The foot helps molluscs to move and in gastropods it make mucus that the animal slides along.Visceral mass includes the gills, guts, and other organs in the center of an mollusk's body