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: humans use lipids to store energy. 
Question: what uses lipids to store energy?
[A]: humans.


[Q]: Fact: nails prevent water loss. 
Question: what do nails prevent?
[A]: water loss.


[Q]: Fact: mitosis often causes growth. 
Question: What causes growth sometimes?
[A]:
Mitosis.