Given a scientific question and its correct answer, generate supporting facts for the answer. This supporting fact can be an explanation for the answer to the given question.

Example input: Question: What term refers to a list of the elements that will replace the ones below them in single-replacement reactions? Answer: activity series
Example output: A list called the activity series does the same thing the periodic table does for halogens: it lists the elements that will replace elements below them in single-replacement reactions.
Example explanation: This is a valid supporting statement since it connects both the answers and question to generate the supporting fact
Q: Question: Where does digestion take place within an incomplete digestive system? Answer: gastrovascular cavity
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
Flatworms have an incomplete digestive system. This means that the digestive tract has only one opening. Digestion takes place in the gastrovascular cavity.