The correct option is D Odontoblasts
Dentin is the substance beneath the tooth enamel and secreted by the odontoblast cells. The formation of dentin by the odontoblast cells is known as dentinogenesis.
Osteoblasts are the cells required for the synthesis of bone.
Calcoblasts or the scleroblasts are the spicules which protrude out from the sponge-sycon.
Chondriocytes are the cells required for the synthesis of cartilagenous matrix, which consists of collagen and proteoglycans mainly.