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: the looseness of soil increases the amount of oxygen in that soil.
Example Output: increases the amount of oxygen in that soil.

Example Input: Fact: phase changes do not change mass.
Example Output: Phase changes.

Example Input: Fact: the type of material through which sound passes changes the speed at which sound travels.
Example Output:
material speed sound.