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: Telephones are used for communication by transmitting audible waves. 
Question: Telephones are used for communication by transmitting what?

Answer: audible waves.


Question: Fact: a flashlight requires a source of energy to produce light. 
Question: What requires a source of energy to produce light?

Answer: flashlights.


Question: Fact: Lightning can cause a wildfire. 
Question: What can cause a wildfire?

Answer:
lightning.