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: a flashlight requires a source of energy to produce light. 
Question: What requires a source of energy to produce light?
[A]: flashlights.


[Q]: Fact: cell division is how humans grow and repair themselves. 
Question: what uses cell division to grow and repair themselves?
[A]: humans.


[Q]: Fact: Cell phones are used for communication by two people by transmitting sound. 
Question: What are used for two people for communication with sound?
[A]:
cell phones.