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.

[EX Q]: Fact: Heat is necessary for the survival of animals. 
Question: What is necessary for the survival of animals?
[EX A]: heat.

[EX Q]: Fact: If something is black then it absorbs all different wavelengths of light. 
Question: If something is what, then it absorbs all different wavelengths of light?
[EX A]: black.

[EX Q]: Fact: Antigens are molecules that the immune system recognizes as needing to be rejected from the body. 
Question: Antigens are molecules that the immune system recognizes as needing to be what?
[EX A]:
rejected from the body.