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.

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

Fact: x-rays are used in oncology. 
Question: what are used in oncology?
x-rays.

Fact: if an object is kicked then a measurement of newtons is exerted on that object. 
Question: what is exerted on a kicked object?

measurement of newtons.