Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

[EX Q]: Fact: heat is detected by sensory nerve cells. 
Question: What is detected by sensory nerve cells?
[EX A]: heat.

[EX Q]: Fact: A fertilized egg can create an offspring if it's carried until birth. 
Question: When does a fertilized egg become an offspring?
[EX A]: When it's born.

[EX Q]: Fact: Gene flow occurs when individuals migrate. 
Question: Migration increases what?
[EX A]:
gene flow.