The correct option is D spicules
Sponges belongs to phylum Porifera. Their body is supported by a skeleton made up of spicules or spongin fibres. Phylum Porifera exhibits characteristic body structure made of a loose aggregate of cells, internal cavities canals lined with food filtering flagellated cells, called the choanocytes. These are also called the collar cells and are a characteristic feature of this phylum.
Ostia are small pores or openings found on the surface of the sponges.
Spongocoel is the large central cavity present in the body of sponges.