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.

Example Input: Fact: Coal is used to produce the movement of electrons by burning in coal-fire power stations. 
Question: Coal is used to produce the movement of electrons by what in coal-fire power stations?
Example Output: burning.

Example Input: Fact: incinerated mercury can cause the ph of soil to decrease. 
Question: what can cause the ph of soil to decrease?
Example Output: incinerated mercury.

Example Input: Fact: Radiators use oil to heat buildings. 
Question: What do radiators use to heat buildings?
Example Output:
Oil.