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: producing thrust causes something to move.
engines produce thrust.

Fact: Insects may live in large colonies and have complex social behaviors.
insect arthropod.

Fact: the Earth being tilted on its rotating axis causes seasons.

Seasons are annual.