The correct option is B Ruben
Ruben along with Kamen demonstrated that oxygen evolved during photosynthesis comes from water and not from carbon dioxide.
R. Mayer proposed that green plants convert solar energy into chemical energy during the process of photosynthesis.
Blackman propounded the ‘law’ or principle of limiting factors.
Calvin mapped the complete route that carbon travels through a plant during photosynthesis, which is called the calvin cycle.