Isotopes popularly known to have been used in the study of photosynthesis are

• A
  $C^{14}$ and $O^{18}$
• B
  $C^{11}$ and $P^{32}$
• C
  $O^{16}$ and $N^{15}$
• D
  $P^{32}$ and $C^{15}$