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.

Q: Fact: When heat passes through metal, that metal expands. 
Question: What happens to metal when heat passes through it?

A: It expands.
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Q: Fact: Passenger pigeons could not produce enough offspring. 
Question: What could not produce enough offspring?

A: passenger pigeons.
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Q: Fact: Rhizobial bacteria converts nitrogen into a fertilizer for plants. 
Question: What does rhizobial bacteria do for plants?

A:
Converts nitrogen.
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