instruction:
In this task, you are given a question and an answer, you would be asked to create the sentence based on the Question-Answer provided. It should be contained within the Question-Answer provided.
question:
Question: What sort of digestion do animals engage in? Answer: internal
answer:
Animals engage in internal digestion.


question:
Question: Corals build hard exoskeletons that grow to become what? Answer: coral reefs
answer:
Corals build hard exoskeletons that grow to become coral reefs.


question:
Question: Which of these is the BEST sign that the fall season has begun? Answer: Leaves changing color on trees
answer:

Leaves changing color on trees of these is the best sign that the fall season has begun.