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.
--------
Question: Fact: the moon revolving around the Earth causes the new moon. 
Question: the moon revolving around the Earth causes what?

Answer: new moon.


Question: Fact: Exposure to cold can induce many muscle fibers to contract at once. 
Question: Many muscle fibers contracting at once can be induced by?

Answer: exposure to cold.


Question: Fact: objects will sink between boundaries with different densities due to gravity. 
Question: objects will sink between boundaries with different what due to gravity?

Answer:
densities.