Question

Which helped in confirming that oxygen evolved in photosynthesis comes from water

• A. $H_2^{18}O$
  
• B. ${}^{14}C{O}_2$
  
• C. ${}^{15}N{O}_3$
  
• D. ${}^3{H}_{2}O$

Answer 1

The correct option is A $H_2^{18}O$


Cornelius van Niel in 1931, demonstrated that photosynthesis is a light-dependent reaction and proposed that oxygen that is evolved during photosynthesis originates from water.
Ruben and Kamen's photosynthesis experiment using heavy isotope of oxygen ${}^{18}O$ in water, to yield ${}^{18}{O}_2$ gas confirmed this hypothisis.