Question

A land snail, a clam, and an octopus all share:
A. A mantle
B. A radula
C. Embryonic torsion
D. Distinct cephalization

Answer 1

Hint:Molluscs belong to an important phylum of invertebrate animals. Most of the molluscs are marine while many are in-shore, which is why they stay in shallow water. Molluscs are the largest marine phylum. Some of them are also seen in freshwater and on land. Molluscs have great diversity.

Complete answer:Mantle- Mantle is a significant anatomy part of the molluscs: This part is the dorsal wall of the body which will cover the visceral mass and they are protruded in the form of flaps. This secretes calcium carbonate and conchiolin and they create shell-like structure.
Radula- Radula is an anatomical structure of molluscs and they are used for feeding basically like a tongue. This structure has a minute tooth which is used for cutting or scraping food.
Embryonic torsion- Torsion is twisting. It is the rotation of visceral organs to an angle of 180 degrees in anticlockwise motion during larval development.
Distinct cephalization- Cephalization is the process in which the organisms develop a distinct head. A cephalized organism will have a very dense group of nerves or brain that controls the body and they have specialized organs for perception and consumptions like eyes, ears, and mouth. They have a distinct division of bodies like the top, front, back.
Hence the answer is option A, a mantle.

Note: The two unique features of mollusks are that they have a mantle and a radula. The mantle is a tissue that lies between the body and the shell. It secretes calcium carbonate which will lead to the formation of shell. They form a mantle cavity that is between the body and the shell. This cavity will pump water to filter-feeding. The radula is the organ that is for feeding which is fitted with a tooth made up of chitin.