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: one-celled animals make humans sick when they become parasites. 
Question: what can make humans sick when they become parasites?

Answer: one-celled animals.


Question: Fact: Birds have backbones. 
Question: What animals have a backbone?

Answer: Birds.


Question: Fact: lightning ignites fires. 
Question: what can lightning ignite?

Answer:
fires.