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.

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

[EX Q]: Fact: a ruler is used for measuring the length of an object.
[EX A]: Length of object.

[EX Q]: Fact: when a river floods , that river deposits soil in flood plains.
[EX A]:
flood cause.