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.

[Q]: Fact: lightning ignites fires. 
Question: what can lightning ignite?
[A]: fires.


[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?
[A]: natural aphrodisiacs.


[Q]: Fact: Any protein that causes an allergy is called an allergen. 
Question: If what causes an allergy it is called an allergen?
[A]:
Protein.