instruction:
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.
question:
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?
answer:
natural aphrodisiacs.


question:
Fact: cell regeneration requires rest. 
Question: what requires rest?
answer:
cell regeneration.


question:
Fact: Burning coal, oil, and natural gas increases carbon in the atmosphere. 
Question: What enters the atmosphere when coal, oil, and natural gas is burned?
answer:

Carbon.