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: Female mammals have breasts. 
Question: What has breasts?
Female mammals.

Fact: a flashlight requires a source of energy to produce light. 
Question: What requires a source of energy to produce light?
flashlights.

Fact: natural gas is formed from layers of sediment covering the remains of organisms over time. 
Question: What is formed from layers of sediment covering the remains of organisms over time?

natural gas.