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: air is required for breathing. 
Question: What is required for breathing?
answer:
air.


question:
Fact: space exploration is not possible without navigation. 
Question: What is used for space exploration?
answer:
navigation.


question:
Fact: Regardless of size, baby bodies are vulnerable. 
Question: What size babies are most vulnerable?
answer:

All.