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: animals use sound to find a mate. 
Question: What do animals use to find a mate?
sound.

Fact: The bonds of that which when heavy is Deuterium cause water to expand when it freezes. 
Question: The bonds of that which when heavy is Deuterium cause what to expand when it freezes?
water.

Fact: Many consumers feed at more than one nutrient level. 
Question: Many consumers feed at more than one what?

nutrient level.