The correct option is D Joseph Priestley
Priestley made a significant observation through a series of experiments: A fire would douse itself and a mouse would choke out when set in the sealed container. Nonetheless, putting a green plant in the container and presenting it to daylight would allow the fire to stay lit and the mouse to stay alive.
Later, he discovered that plants discharge oxygen into the air during photosynthesis.
On August 1, 1774, Priestley performed the famous experiment which led to the discovery of oxygen. Utilizing a 12-inchwide glass lens, he centered daylight on a piece of mercuric oxide in a reversed glass holder set in a pool of mercury. The colorless, unscented, tasteless, dull gas radiated from the flame made fire more intense and kept a mouse alive. Thus oxygen was discovered.
Jan Ingenhousz demonstrated that sunlight was necessary for photosynthesis by placing a similar set up that was used by Priestley, once in the dark and the other time in the sunlight.
Julius von Sachs in 1854 found that starch is the primary visible result of photosynthesis.
Theodore de Saussure was instrumental in showing that carbon dioxide was consumed by the plants during photosynthesis.