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.

Input: Consider Input: Fact: Creatures with feathers and wings have a large brain relative to the size of their body. 
Question: Creatures with feathers and wings have a large brain relative to the size of their what?

Output: body.


Input: Consider Input: Fact: All birds have backbones. 
Question: Which animal has a backbone?

Output: bird.


Input: Consider Input: Fact: Hydrogen ions change the color of litmus paper from blue to red. 
Question: What changes the color of litmus paper from blue to red?


Output: hydrogen ions.