The correct option is C Pinctada
The body of molluscs is covered and protected by a calcareous shell.
Pinctada and Octopus belong to phylum Mollusca. Pinctada is pearl oyster and has a bivalve shell. Octopus is an exception in phylum Mollusca as it does not have a shell.
Cucumaria (sea cucumber) and Ophiura (brittle star) belong to phylum Echinodermata. Members of phylum Echinodermata do not have shells.