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.

Input: Consider Input: Fact: Bulbs require electrical energy to see in darkness. 
Question: Bulbs produce electrical energy to what?

Output: see in darkness.


Input: Consider Input: Fact: The crystallized rocks are made by lava from the mantle. 
Question: Where does the lava come from that makes igneous rocks?

Output: Mantle.


Input: Consider Input: Fact: humans generate heat mainly by keeping their metabolic rate high. 
Question: what generates heat mainly by keeping their metabolic rate high?


Output: humans.