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: pines have a positive impact on an ecosystem. 
Question: what has a positive impact on an ecosystem?
answer:
pines.


question:
Fact: heat is detected by sensory nerve cells. 
Question: What is detected by sensory nerve cells?
answer:
heat.


question:
Fact: a generator uses fossil fuel. 
Question: what does a generator use?
answer:

fossil fuel.