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: decomposition increases amount of organic matter in dirt. 
Question: What increases amount of organic matter in dirt?

Answer: decomposition.


Question: Fact: Taste and smell have a positive impact on  an animal's survival. 
Question: What has a positive impact on animal's survival?

Answer: taste and smell.


Question: Fact: Something that is exogenous can be used to estimate the age of a tree. 
Question: What can be used to estimate the age of a tree?

Answer:
Something that is exogenous.