The correct option is C Mantle
Mollusca is the second largest phylum after Arthropoda. The shell of mollusc is composed of calcium carbonate. It encloses, supports and protects the soft parts of an animal in the phylum of Mollusca. It is formed, repaired and maintained by a mantle. mantle cavity is a fold in the mantle which mainly encloses the soft body. So, the correct answer is option C.