What do mollusks have in common?

* Body: Mollusks have a soft body that is protected by a hard shell. The shell is made of calcium carbonate and is secreted by the mollusk's mantle.

* Mantle: The mantle is a fleshy layer of tissue that covers the mollusk's body. The mantle is responsible for secreting the shell and for regulating the mollusk's water balance.

* Foot: Mollusks have a muscular foot that they use to move around. The foot is located on the ventral side of the body and is made of muscles that contract and relax to move the mollusk.

* Visceral mass: The visceral mass is the soft body of the mollusk that is contained within the shell. The visceral mass contains the mollusk's organs, including the heart, stomach, intestines, and reproductive organs.

* Radula: Mollusks have a radula, which is a rasping tongue that they use to scrape food. The radula is made of chitin and is covered in tiny teeth.