The correct option is D Saccoglossus
Proboscis gland is an excretory organ in hemichordates. Of the given options, Saccoglossus is a hemichordate.
Dentalium is a mollusc. Nephridia are excretory organs in molluscs.
Echinus and Cucumaria are echinoderms. In echinoderms, the excretory wastes are removed out of the body by diffusion.