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: carcinogens can cause death. 
Question: What can cause death?
[A]: carcinogens.


[Q]: Fact: human power causes a bike to move. 
Question: What causes a bike to move?
[A]: Human power.


[Q]: Fact: Fungi have special structures for penetrating trees. 
Question: What have special structures for penetrating trees?
[A]:
Fungi.