TASK DEFINITION: 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.
PROBLEM: Fact: the threat of being eaten causes a porcupine to extend its quills. 
Question: What threat would cause a porcupine to extend its quills?

SOLUTION: being eaten.

PROBLEM: Fact: human power causes a bike to move. 
Question: What causes a bike to move?

SOLUTION: Human power.

PROBLEM: Fact: humans can change ecosystems drastically. 
Question: who can change ecosystems drastically?

SOLUTION:
humans.