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: memory cells help keep people from getting sick. 
Question: What helps keep people from getting sick?
[EX A]: Memory cells.

[EX Q]: Fact: Water must not be polluted to be safe. 
Question: What can happen to water to make it unsafe?
[EX A]: Pollution.

[EX Q]: Fact: lactobacillus aids chemical digestion. 
Question: What aids chemical digestion?
[EX A]:
lactobacillus.