The correct option is C Jan Baptist van Helmont
Jan Baptist van Helmont performed willow tree experiment to demonstrate that water was essential for the plants to perform photosynthesis, which, inturn was required for the growth and development of them. He refuted the claims of people who believed that plants ate soil to increase their biomass.
In his willow tree experiment, Helmont recorded the initial weight of a willow tree sapling and the soil which was used to plant the sapling. By watering the plant, he nurtured it for a span of five years. Then, he recorded the final weight of the tree and the soil in which it grew. He observed that the weight of the soil almost remained the same while the final weight of the plant was found to be 33 times greater than its initial weight. This helped him to conclude that plants did not eat soil, instead, depend on water and mineral salts from the soil to increase their biomass.
Jan Ingenhousz was instrumental in proving that sunlight was essential for photosynthesis by performing aquatic plant experiment. He was also able to infer that only the green parts of the plants performed photosynthesis and released oxygen. In his aquatic plant experiment, green parts of the aquatic plant released oxygen in the form of bubbles.
Nicolas Theodore De Saussure performed an experiment to prove that plants absorbed carbon dioxide along with other components like water and mineral salts to increase their biomass. He helped to assert the importance of carbon dioxide in photosynthesis.
Joseph Priestley was instrumental in the discovery of oxygen. He performed the bell jar experiment to demonstrate that plants produced oxygen during the process of photosynthesis.