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: When heat passes through metal, that metal expands. 
Question: What happens to metal when heat passes through it?
[EX A]: It expands.

[EX Q]: Fact: A vehicle in use requires navigation. 
Question: A vehicle in use requires?
[EX A]: navigation.

[EX Q]: Fact: a decrease in differentiation tends to occur when individuals move in and out of a population. 
Question: What tends to occur when individuals move in and out of a population?
[EX A]:
a decrease in differentiation.