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: memory cells help keep people from getting sick. 
Question: What helps keep people from getting sick?
Example Output: Memory cells.

Example Input: Fact: navigation requires knowing which way to go. 
Question: What requires knowing which way to go?
Example Output: navigation.

Example Input: Fact: Antibodies are large, Y-shaped proteins that recognize and bind to immunogens. 
Question: Antibodies are large, Y-shaped proteins that recognize and bind to?
Example Output:
immunogens.