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: Heat is necessary for the survival of animals. 
Question: What is necessary for the survival of animals?
answer:
heat.


question:
Fact: chemical weathering causes iron to turn brown, red, or orange. 
Question: What does chemical weather cause iron to do?
answer:
Change color to brown.


question:
Fact: Sex hormones carry signals that control sexual development and reproduction. 
Question: _ carry signals that control sexual development and reproduction.?
answer:

sex hormones.