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: A bill is used for catching prey by some birds. 
Question: What is used by some birds to catch their prey?

Answer: a bill.


Question: Fact: Beavers cause ponds and lakes to form. 
Question: What can be the cause of lakes and ponds forming?

Answer: beavers.


Question: Fact: Plants grow better when surrounding trees fall. 
Question: What do plants do when a tree nearby falls?

Answer:
They grow better.