The thin, spiny structure that form the skeleton of a sponge

The spicules are the thin and spiny structure that forms the skeleton of a sponge. The spicules provide the structural support and they are small needle-like in a shape. The spicules consist of calcium carbonate and silicon dioxide. It is found in many sponges of the skeleton, they are basically like crystals and they have a pointed and hard and sharp body. Like animals, the sponges also posses some sort of skeleton which gives shapes to their body. The skeletal system of the sponge is like a needle or cluster in shape.

the trilobite is used as an index fossil for various geologic time periods as specific types of the trilobites were present in different geological time periods. they are a group of marine arthropods belonging to the class of trilobita.

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the answer is c

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