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.

Fact: a refrigerator is used for keeping food fresh for a long period of time.
food chicken.

Fact: if an object is made of a material then that object has the properties of that material.
Material is a substance.

Fact: a cactus stem is used for storing water.

cactus desert plant.