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.

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

Output: exposure to cold.


Input: Consider Input: Fact: Heating with coal can cause air pollution. 
Question: Heating with coal can cause?

Output: air pollution.


Input: Consider Input: Fact: most unicellular organisms move with flagella. 
Question: What helps unicellular organisms move?


Output: flagella.