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: High pressure systems cause calm weather conditions. 
Question: High pressure systems cause what weather conditions?
[A]: calm.


[Q]: Fact: mammals keep warm with hair. 
Question: what do mammals keep warm with?
[A]: hair.


[Q]: Fact: diffusion requires energy. 
Question: What requires energy?
[A]:
diffusion.