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: Some mollusks are not easily seen with the naked eye. 
Question: What are not easily seen with the naked eye?
answer:
mollusks.


question:
Fact: Water can make soil from rocks. 
Question: What causes rocks to be worn into soil?
answer:
Water.


question:
Fact: organisms rely on a relative narrow range of acidity. 
Question: what relies on a relatively narrow range of acidity?
answer:

organisms.