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: barometric pressure makes clear weather. 
Question: What causes clear weather?

Answer: barometric pressure.


Question: Fact: Hummingbirds co-evolved with plants. 
Question: Hummingbirds are what they are today as a necessary consequence of their relationship to what?

Answer: Plants.


Question: Fact: stems hold nutrients in plants. 
Question: what do stems hold in plants?

Answer:
nutrients.