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: navigation requires knowing which way to go. 
Question: What requires knowing which way to go?
answer:
navigation.


question:
Fact: Any surface that has not been sterilized will produce substances that are toxic. 
Question: What will produce substances that are toxic?
answer:
a surface not sterilized.


question:
Fact: darkness has a negative impact on plant growth. 
Question: What has a negative impact on plant growth?
answer:

darkness.