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: vein deposits of gold and silver are formed by igneous intrusion.
[EX A]: gold and silver are valuable.

[EX Q]: Fact: Insects generally have two pairs of wings for flight.
[EX A]: dragonflies are insects.

[EX Q]: Fact: Lymph is a fluid that leaks out of capillaries into spaces between cells.
[EX A]:
capillaries.