The correct option is A Priestly
Priestly performed the classic bell jar experiment to demostrate that plants produced oxygen.
van Niel proposed that oxygen produced during photosynthesis came from water rather than from carbon dioxide.
Ingenhousz demonstrated that the green parts of the plants like the stems and leaves, could manufacture oxygen by using the Sun’s light and not its heat.
Engelmann discovered that photosynthesis occurs in the chloroplast.