The correct option is C Priestley
J. Priestley (1772) carried out very interesting experiment on Bell jar, rat, pudina or mint and candle. He came to conclude that plants purify air (burning of candles), and gaseous exchange occurs during photosynthesis.
Priestley observed that a candle burning in a closed space – a bell jar, soon gets extinguished. Similarly, a mouse would soon suffocate in a closed space. He concluded that a burning candle or an animal that breathe the air, both somehow, damage the air. But when he placed a mint plant in the same bell jar, he found that the mouse stayed alive and the candle continued to burn. Priestley hypothesized as follows: Plants restore the air which breathing animals and burning candles remove.
Prof Richard Martin Willstatter was a German organic chemist who study the structure of plant pigments, chlorophyll.
Robert Hooke was an English scientist who was the first to visualize a micro-organism using a microscope.
Jean Senebier was a Genevan Calvinist pastor and naturalist.He wrote extensively on plant physiology.
So the scientist who first pointed out that plants purify foul air by bell jar experiment was Priestley.