Generate a sentence that answers this question: "John was able to read at night even though the electricity had gone out. John was using".

Answer: a candle is a source of light when it is burned

Generate a sentence that answers this question: "Light produced by deep sea animals is used for?".

Answer: producing light is used for attracting prey by some deep sea animals

Generate a sentence that answers this question: "in order for utility of a tool to occur, what has to happen first?".

Answer:
inventing a tool allows that tool to be used