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: Most animals without backbones have a nervous system. 
Question: Which type of system do most animals without backbones have?
Example Output: Nervous system.

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

Example Input: Fact: Limestone interacting with wind over long periods of time causes weathering. 
Question: What causes weathering when interacting with wind?
Example Output:
limestone.