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: Using hydropower reduces greenhouse gases. 
Question: What does hydropower help reduce?
Greenhouse gases.

Fact: Earth's magnetic patterns are used for finding locations of birds and fish. 
Question: what is Earth's magnetic patterns used for finding the locations of?
birds and fish.

Fact: Preservatives are added to food to prolong it's shelf life. 
Question: What prolongs the storage life of food in space?

preservatives.