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: Viruses are viewed by illuminating electrons. 
Question: What of the following can only be viewed by illuminating electrons?
[A]: viruses.


[Q]: Fact: Sight is the ability to see when light allows an image to be focused on the retina. 
Question: What is it called when light allows an image to be focused on the retina?
[A]: Sight.


[Q]: Fact: Incandescent bulbs produce heat as they create electricity. 
Question: What do incandescent bulbs produce as they create electricity?
[A]:
heat.