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.

[EX Q]: Fact: Most ecosystems get energy from sunlight.
[EX A]: ecosystem habitat.

[EX Q]: Fact: Amphibians are the first true tetrapods, or vertebrates with four limbs.
[EX A]: Amphibians.

[EX Q]: Fact: Mutations are essential for evolution to occur.
[EX A]:
Evolution.