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.

Fact: oxygen is essential for cellular respiration for fungi. 
Question: what requires oxygen for cellular respiration?
fungi.

Fact: penguins are endothermic tetrapod vertebrates. 
Question: what are endothermic tetrapod vertebrates?
penguins.

Fact: Ethanol is used to produce electricity by burning. 
Question: What is burning ethanol used to produce?

electricity.