Here's why:

* Coelom: Annelids possess a true coelom, a fluid-filled body cavity lined with mesoderm. This is a key characteristic that sets them apart from other worm-like organisms.

* Clitellum: The clitellum is a thickened band on the body of some annelids that plays a role in reproduction. Its presence is a strong indicator of belonging to this phylum.

While other worm-like organisms might share some features, the combination of a coelom and a clitellum strongly points towards an annelid. Examples of annelids include earthworms, leeches, and marine polychaetes.