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: Bulbs require electrical energy to see in darkness. 
Question: Bulbs produce electrical energy to what?
see in darkness.

Fact: Mutations can be detected by analysis on gene abnormalities. 
Question: Which process of gene abnormalities can mutations be detected?
analysis.

Fact: pouring salt on an icy doorstep will reduce the melting point of the ice, making it easier to remove as the ice changes from a solid to a liquid at a lower temperature. 
Question: Why is it useful to pour salt on an icy doorstep?

The salt will decrease the melting point of the ice, making it easier to remove the ice after the solid begins to turn into a liquid.