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: protective plates over the ends of the fingers become more brittle with age. 
Question: What do fingers have over the ends that become more brittle with age?

Output: protective plates.


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

Output: fires.


Input: Consider Input: Fact: Phylogeny is full of dead-ends and false starts. 
Question: What is a challenge in phylogeny?


Output: Dead-ends and false starts.