instruction:
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: water flow through soil is variable. 
Question: What is the rate of water flow of soil?
answer:
variable.


question:
Fact: humans require energy for growth. 
Question: what requires energy for growth?
answer:
humans.


question:
Fact: a cactus stem is used for storing H2O. 
Question: A cactus stem stores what?
answer:

h2o.