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: Water can make soil from rocks. 
Question: What causes rocks to be worn into soil?
[A]: Water.


[Q]: Fact: a platypus lacks a uterus. 
Question: What do platypuses not have?
[A]: uterus.


[Q]: Fact: webbed feet are used for moving faster through water by ducks. 
Question: what uses webbed feet for moving faster through water?
[A]:
ducks.