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: pesticides cause pollution.
Example output: pollution harms.
Example explanation: This is a good topic word, because it contains one overlapping word "pollution".
Q: Fact: Complex chemistry is needed to carry out all the functions of life.
A:
Complex chemistry.