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Which animal has thorns of calcium carbonate on its body?
A. Lungfish
B. Snail
C. Sponge
D. Starfish.

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Last updated date: 13th Jun 2024
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Answer
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Hint: This animal also known as crown-of-thorns as it receives this name from venomous thorn-like spines that cover its upper surface, resembling the biblical crown of thorns. The body form of this animal has a central disk and radiating arms.

Complete answer:
To answer this question, first, we need to know about animals which have thorns of calcium carbonate such as starfish. The extended pointed spines are present on the sides of the starfish's arms and abdominal surface similar to thorns and form a crown-like shape based on that it is named as crown of thorns. The spines are hard and very sharp, and readily pierce through soft surfaces. Despite the battery of sharp spines on the aboral surface and blunt spines on the oral surface, the crown-of-thorns starfish's general body surface is membranous and soft.
 Now, let us find the solution from the option.
Molluscs have calcium carbonate exoskeleton in their bodies. Snails are molluscs and carry a shell on their body composed of calcium carbonate. Lungfish, sponge, and starfish do not have calcium carbonate deposited on their bodies.
Lungfish, snail and sponge do not have any calcium carbonate thorns or spins on its body.

Thus, the correct option is D. i.e. Starfish.

Note:Adult crown-of-thorns starfish normally range in size from 25 to 35 cm (9.8 to 13.8 in). The body of the crown of thorns has a rigid structure, it is capable of mixing and changing to fit over the shapes of the corals on which it consumes food. When the starfish is taken out from the water, the body surfaces are damaged and the body liquid comes out, so the body falls down and becomes flat, also spines curve over and flat structure.