In this task, you need to write a topic word from the given fact. The topic word must have at least one word overlap with the given fact. The topic word often involves adding a new word from a related concept. In your topic word, use at least one word from the given fact. Topic words with two or more words work best.

Q: Fact: a refrigerator is used for keeping food fresh for a long period of time.

A: food chicken.
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Q: Fact: burning fossil fuels increases the carbon in the atmosphere.

A: carbon atmosphere.
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Q: Fact: Muscle contraction occurs when muscle fibers get shorter.

A:
Muscle contraction.
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