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: coal is used for generating heat by burning.
[A]: burning coal pollution.


[Q]: Fact: Bone is less flexible than cartilage but stronger.
[A]: bone cartilage.


[Q]: Fact: heating salt water causes the water to evaporate while the salt remains.
[A]:
boiling water evaporate.