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: sand dunes are formed by the wind transporting and depositing sand.

A: sand dune formation desert.
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Q: Fact: chlorophyll is used for absorbing light energy by plants.

A: chlorophyll all green plants.
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Q: Fact: damming a river can cause a lake to form.

A:
beaver dam.
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