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

Output: Active immunity.


Input: Consider Input: Fact: nuclear reactions in stars causes stars to produce light.

Output: light contains photons.


Input: Consider Input: Fact: All animals are heterotrophs.


Output: All animals are heterotrophs.