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: Carbon monoxide is a gas produced by furnaces and other devices that burn fuel.

A: Carbon monoxide.
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Q: Fact: Hair is a fiber that is found only in mammals.

A: hair auburn.
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Q: Fact: Most invertebrates have a more complex nervous system.

A:
Invertebrates.
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