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: Thyroxine increase the rate of metabolism in cells throughout the body. 
Question: What increases the rate of metabolism in cells throughout the body?
[EX A]: Thyroxine.

[EX Q]: Fact: Water can make soil from rocks. 
Question: What causes rocks to be worn into soil?
[EX A]: Water.

[EX Q]: Fact: fluoride prevents destruction of tooth enamel. 
Question: fluoride in toothpaste prevents destruction of what?
[EX A]:
tooth enamel.