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: the vomiting reflex is used to remove toxic material from the stomach before it is absorbed.
[EX A]: vomit toxic.

[EX Q]: Fact: Many corals secrete an exoskeleton that builds up to become a coral reef.
[EX A]: coral exoskeleton is made of carbonate.

[EX Q]: Fact: sinkholes are formed by precipitation.
[EX A]:
precipitation are formed by.