Final answer:
Acorn worms have a complete digestive system with a mouth and an anus. The digestive system includes a pharynx, intestine, and anus.
Step-by-step explanation:
Acorn worms have a complete digestive system, which means they have a mouth and an anus. This type of digestive system allows for more efficient digestion and specialization of digestive functions. Acorn worms have a mouth opening that leads into the pharynx, followed by the intestine, which ends in an anus. The digestive system of acorn worms is similar to that of many other annelids, such as earthworms and leeches.