instruction:
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: warblers are nocturnal and travel long distances at night. 
Question: What are nocturnal and travel long distances at night?
answer:
warblers.


question:
Fact: muscles contain cells. 
Question: What do muscles contain?
answer:
cells.


question:
Fact: radiation can cause cancer. 
Question: Which of the following can cause cancer?
answer:

radiation.