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

Answer: being eaten.


Question: Fact: Pollen grains are small male reproductive bodies of plants used to pollinate female flowers. 
Question: pollen grains are small male reproductive bodies of plants used to pollinate what?

Answer: female flowers.


Question: Fact: Unequal heating of the Earth's surface by the Sun causes tropical wind and ocean circulation. 
Question: Unequal heating of the Earth's surface by the Sun causes ocean circulation and what?

Answer:
tropical wind.