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.

[Q]: Fact: a circle graph can be used to display percents.
[A]: Graphs are made of.


[Q]: Fact: Mutations that lead to cancer usually occur in genes that control the cell cycle.
[A]: cancer leukemia.


[Q]: Fact: phase changes do not change mass.
[A]:
Phase changes.