Answer the following question given this paragraph: Segmented worms have a well-developed body cavity filled with fluid. This fluid-filled cavity serves as a hydroskeleton , a supportive structure that helps move the worm's muscles. Only the most primitive worms (the flatworms) lack a body cavity. Q: What is the name of the supportive structed that helps move a worm's muscles? Choices: - spongin - exoskeleton - pollenation - hydroskeleton A:
Answer:
hydroskeleton