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.

[EX Q]: Fact: navigation requires knowing which way to go. 
Question: What requires knowing which way to go?
[EX A]: navigation.

[EX Q]: Fact: male dogs use natural aphrodisiacs in urine to mark their territory. 
Question: what do male dogs use in their urine to mark their territory?
[EX A]: natural aphrodisiacs.

[EX Q]: Fact: friction causes the volume of an object to increase. 
Question: Friction causes an increase  of an object's?
[EX A]:
volume.