Write a correct answer to the given question based on its associated fact. Make sure that your answer is contained in the associated fact. Don't be creative and introduce any new word that is not mentioned in the associated fact! Remember that the associated fact has been rearranged to form the question. So, the correct answer words must lie within the associated fact. The correct answer can be a word, phrase, or even a sentence.

Fact: Absorbing energy causes metal objects to expand. 
Question: Metal expands when it does what?
absorbs energy.

Fact: A thing arranged in clusters mostly contain instructions for a single protein. 
Question: How often does a thing arranged in clusters contain instructions for a single protein?
mostly.

Fact: Weathering causes a river to become deeper and wider. 
Question: Weathering causes what to become deeper and wider?

a river.