The correct option is C Pelecypoda
Pelecypoda includes the bivalves, clams, oysters and mussels. They are bilaterally symmetrical and laterally compressed. The oysters, clams and scallops are a major source of human food. The shells of freshwater clams particularly have been used for buttons. Pearls are secretions of the mantle around an irritant of calcium carbonate and are usually found in some oyster species. So, the correct answer is option C.