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.

Example Input: Fact: Mutation creates new genetic variation in a gene pool.
Example Output: gene pool.

Example Input: Fact: if an object reflects light toward the eye then that object can be seen.
Example Output: light beams.

Example Input: Fact: a breathing mask is used for keeping harmful particles from entering the respiratory system.
Example Output:
air particles.