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.

Fact: eyes are used for seeing by animals by sensing light.
animal mammals.

Fact: Amphibians are also important predators.
amphibian predator.

Fact: most canyons are formed by flowing rivers through erosion over long periods of time.

Erosion is.