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.

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

Output: flashlights.


Input: Consider Input: Fact: force causes the speed of a crystal ball to increase. 
Question: What can force affect the speed of?

Output: a crystal ball.


Input: Consider Input: Fact: carbon polymorphs are used for making pencil lead. 
Question: what is used for making pencil lead?


Output: carbon polymorphs.