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.

[Q]: Fact: amoebae have motility. 
Question: what have motility?
[A]: amoebae.


[Q]: Fact: A vehicle in use requires navigation. 
Question: A vehicle in use requires?
[A]: navigation.


[Q]: Fact: Constriction happens when the muscular walls of arteries and veins contract. 
Question: What happens when muscular walls of arteries and veins contract?
[A]:
constriction.