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.

[EX Q]: Fact: Blowing air into a whistle causes air to move inside the whistle. 
Question: Blowing air into what causes air to move inside it?
[EX A]: whistle.

[EX Q]: Fact: Cells that divide uncontrollably may form masses of neoplastic origin. 
Question: Cells that divide uncontrollably may form _.?
[EX A]: masses of neoplastic origin.

[EX Q]: Fact: protein is necessary for cell growth. 
Question: what is required for cell growth?
[EX A]:
protein.