Final answer:
The mantle is responsible for secreting the shell found in Mollusks.
Step-by-step explanation:
The mantle is responsible for secreting the shell found in Mollusks. The mantle is a layer of tissue that lies between the shell and the body. It secretes calcium carbonate to form the shell and covers the body, forming a mantle cavity. Some mollusks, like oysters and mussels, can secrete a calcareous nacre or "mother of pearl" around foreign particles in the mantle cavity, which is commercially exploited to produce pearls.