The correct option is C plants produce oxygen
∙ Joseph Priestly was the first person to show that plants release oxygen. He demonstrated this by performing the classic bell jar experiments.
∙ He demonstrated that when a candle was lit under a bell-jar, it would be put off in a while unless it is placed along with a green plant. Thus, he showed that the green plants produced something that keeps the candle lit, which was later discovered to be oxygen.