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.

Input: Consider Input: Fact: Many corals secrete an exoskeleton that builds up to become a coral reef.

Output: coral exoskeleton is made of carbonate.


Input: Consider Input: Fact: Active immunity results when an immune response to a pathogen produces memory cells.

Output: Active immunity.


Input: Consider Input: Fact: a mirror is used for reflecting light.


Output: light rays.