Final answer:
Acorn worms have a proboscis in front of their mouth that they use for feeding and respiration. The mouth leads to a muscular pharynx and intestine.
Step-by-step explanation:
Acorn worms, also known as enteropneusts, have a mouth located at the anterior end of their body. In front of their mouth, they have a structure called a proboscis. The proboscis is a long, tubular organ that can be extended to capture prey or filter food particles from the surrounding water. It is used for feeding and also serves as a respiratory organ. The mouth leads to a muscular pharynx and intestine, which eventually leads to the anus located at the posterior end of their body.