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: Gene flow occurs when individuals move into or out of a population.
[EX A]: Gene flow.

[EX Q]: Fact: Mollusks are invertebrates such as the common snail.
[EX A]: common snail garden shell.

[EX Q]: Fact: some animals' fur grows thicker for staying warm in the winter.
[EX A]:
animals fur grows thicker.